diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..c1d82d8
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module projekt_gutenberg_de_dl
+
+go 1.16
+
+require github.com/PuerkitoBio/goquery v1.7.1
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..986201f
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,12 @@
+github.com/PuerkitoBio/goquery v1.7.1 h1:oE+T06D+1T7LNrn91B4aERsRIeCLJ/oPSa6xB9FPnz4=
+github.com/PuerkitoBio/goquery v1.7.1/go.mod h1:XY0pP4kfraEmmV1O7Uf6XyjoslwsneBbgeDjLYuN8xY=
+github.com/andybalholm/cascadia v1.2.0 h1:vuRCkM5Ozh/BfmsaTm26kbjm0mIOM3yS5Ek/F5h18aE=
+github.com/andybalholm/cascadia v1.2.0/go.mod h1:YCyR8vOZT9aZ1CHEd8ap0gMVm2aFgxBp0T0eFw1RUQY=
+golang.org/x/net v0.0.0-20180218175443-cbe0f9307d01/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/net v0.0.0-20210614182718-04defd469f4e h1:XpT3nA5TvE525Ne3hInMh6+GETgn27Zfm9dxsThnX2Q=
+golang.org/x/net v0.0.0-20210614182718-04defd469f4e/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..d30bef9
--- /dev/null
+++ b/main.go
@@ -0,0 +1,396 @@
+package main
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"path"
+	"strings"
+
+	gq "github.com/PuerkitoBio/goquery"
+	"golang.org/x/net/html"
+	"golang.org/x/net/html/atom"
+)
+
+var (
+	ErrInvalidURL      = errors.New("invalid url")
+	ErrNoChaptersFound = errors.New("no chapters found in index")
+	ErrParsingPage     = errors.New("error parsing page")
+)
+
+const (
+	colRed    = "\033[31m"
+	colYellow = "\033[33m"
+	colReset  = "\033[m"
+)
+
+func usage(arg0 string, exitStatus int) {
+	fmt.Fprintln(os.Stderr, `Usage:
+  `+arg0+` [options...] <BOOK_URL>
+
+Book URL format:
+  http[s]://[www.]projekt-gutenberg.org/<author>/<book>[/whateverdoesntmatter]
+
+Options:
+  -dir <DIRECTORY>  --  Output directory (default: ".").
+
+Output types:
+  * <INFO>
+  `+colYellow+`! <WARNING>`+colReset+`
+  `+colRed+`! <ERROR>`+colReset)
+	os.Exit(exitStatus)
+}
+
+func printInfo(f string, v ...interface{}) {
+	fmt.Printf("* "+f+"\n", v...)
+}
+
+func printWarn(f string, v ...interface{}) {
+	fmt.Fprintf(os.Stderr, colYellow+"! "+f+colReset+"\n", v...)
+}
+
+func printErr(f string, v ...interface{}) {
+	fmt.Fprintf(os.Stderr, colRed+"! "+f+colReset+"\n", v...)
+	os.Exit(1)
+}
+
+func getBaseUrl(rawurl string) (string, error) {
+	url, err := url.Parse(rawurl)
+	if err != nil {
+		return "", err
+	}
+	if !(url.Scheme == "http" || url.Scheme == "https") {
+		return "", ErrInvalidURL
+	}
+	if !(url.Host == "projekt-gutenberg.org" || url.Host == "www.projekt-gutenberg.org") {
+		return "", ErrInvalidURL
+	}
+	spPath := strings.Split(strings.Trim(url.Path, "/"), "/")
+	if len(spPath) < 2 {
+		return "", ErrInvalidURL
+	}
+	basePath := strings.Join(spPath[:2], "/")
+	return url.Scheme + "://projekt-gutenberg.org/" + basePath, nil
+}
+
+// Returns a slice containing the links to the chapters.
+func getChapters(baseUrl string, doc *gq.Document) ([]string, error) {
+	chapterUrls := make([]string, 0, 8)
+	doc.Find("body ul li").Each(func(i int, s *gq.Selection) {
+		// The website has a strange bug where the 'a' element is separate from
+		// the text element. That's why we have to search the entire 'li'
+		// element for an 'a' element with a link.
+		s = s.Find("a[href]")
+		if len(s.Nodes) == 0 {
+			// This should really never happen, that's why we're using panic.
+			panic("missing link in chapter index")
+		}
+		relUrl, _ := s.Attr("href") // We now know it must have the href attribute.
+		chapterUrls = append(chapterUrls, baseUrl+"/"+relUrl)
+	})
+	if len(chapterUrls) == 0 {
+		return nil, ErrNoChaptersFound
+	}
+	return chapterUrls, nil
+}
+
+type MetaInfo struct {
+	Author string
+	Title  string
+	Year   string
+}
+
+func getMetaInfo(doc *gq.Document) MetaInfo {
+	metas := doc.Find("head meta")
+	return MetaInfo{
+		Author: metas.Filter("[name=\"author\"]").AttrOr("content", "Unknown"),
+		Title:  metas.Filter("[name=\"title\"]").AttrOr("content", "Unknown"),
+		Year:   metas.Filter("[name=\"firstpub\"]").AttrOr("content", "Unknown"),
+	}
+}
+
+func (m MetaInfo) ToTitle() string {
+	return fmt.Sprintf("%s -- %s, %s", m.Author, m.Title, m.Year)
+}
+
+type Extractor struct {
+	BaseUrl     string
+	Meta        MetaInfo
+	ChapterUrls []string
+	W           io.Writer
+}
+
+func NewExtractor(rawurl string, w io.Writer) (*Extractor, error) {
+	baseUrl, err := getBaseUrl(rawurl)
+	if err != nil {
+		return nil, err
+	}
+	return &Extractor{
+		BaseUrl: baseUrl,
+		W: w,
+	}, nil
+}
+
+func (e *Extractor) FetchAndProcessIndex() error {
+	// Get HTML document.
+	resp, err := http.Get(e.BaseUrl)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	// Parse HTML via Goquery.
+	doc, err := gq.NewDocumentFromReader(resp.Body)
+	if err != nil {
+		return err
+	}
+	// Get metadata.
+	metaInfo := getMetaInfo(doc)
+	e.Meta = metaInfo
+	// Get chapter URLs from index.
+	chapterUrls, err := getChapters(e.BaseUrl, doc)
+	if err != nil {
+		return err
+	}
+	e.ChapterUrls = chapterUrls
+	return nil
+}
+
+func (e *Extractor) parseAdditionalPage(doc *gq.Document) error {
+	// Every document has two main <hr> elements with the given properties.
+	// They are a way to mark the contained text.
+	var passedHrs int
+	var err error
+	content := doc.Find("body").Children().FilterFunction(func(i int, s *gq.Selection) bool {
+		if s.Is("hr[size=\"1\"][color=\"#808080\"]") {
+			passedHrs++
+			return false
+		} else if s.Is("a") && (s.Text() == "<<\u00A0zurück" || s.Text() == "weiter\u00A0>>") {
+			// We don't want the "zurück"/"weiter"-buttons
+			return false
+		}
+		switch passedHrs {
+		case 0:
+			return false
+		case 1:
+			return true
+		case 2:
+			return false
+		default:
+			err = ErrParsingPage
+			return false
+		}
+	})
+	if err != nil {
+		return err
+	}
+
+	// Now that we've extracted the actual content, convert it into markdown.
+	var process func(*html.Node) string
+	process = func(n *html.Node) string {
+		processChildren := func() string {
+			var ret string
+			for i := n.FirstChild; i != nil; i = i.NextSibling {
+				ret += process(i)
+			}
+			return ret
+		}
+
+		// Checks if `n` has the given HTML class.
+		hasClass := func(class string) bool {
+			for _, v := range n.Attr {
+				if v.Key == "class" {
+					classes := strings.Split(v.Val, " ")
+					for _, cl := range classes {
+						if cl == class {
+							return true
+						}
+					}
+					return false
+				}
+			}
+			return false
+		}
+
+		var ret string
+		switch n.Type {
+		case html.TextNode:
+			// If we have a text node, return the actual text after some
+			// post-processing.
+			ret = strings.ReplaceAll(n.Data, "\n", "")
+			var newRet string
+			// Replace all sequences of spaces consisting of more than one space
+			// with just one space.
+			var prevWasSpace bool
+			for _, c := range ret {
+				if c == ' ' {
+					if prevWasSpace {
+						continue
+					}
+					prevWasSpace = true
+				} else {
+					prevWasSpace = false
+				}
+				newRet += string(c)
+			}
+			ret = newRet
+		case html.ElementNode:
+			// Transform the individual HTML elements.
+			switch n.DataAtom {
+			case atom.Br:
+				ret = "\n"
+			case atom.H1:
+				ret = "# " + processChildren() + "\n"
+			case atom.H2:
+				ret = "## " + processChildren() + "\n"
+			case atom.H3:
+				ret = "### " + processChildren() + "\n"
+			case atom.H4:
+				ret = "#### " + processChildren() + "\n"
+			case atom.H5:
+				ret = "##### " + processChildren() + "\n"
+			case atom.H6:
+				ret = "###### " + processChildren() + "\n"
+			case atom.P:
+				if hasClass("centerbig") {
+					ret = "#### " + processChildren() + "\n\n"
+				} else {
+					ret = /*"    " + */processChildren() + "\n\n"
+				}
+			case atom.Div:
+				ret = processChildren()
+			case atom.Tt:
+				ret = "`" + processChildren() + "`"
+			case atom.I:
+				ret = "_" + processChildren() + "_"
+			case atom.A:
+				ret = processChildren()
+			case atom.Span:
+				ret = processChildren()
+			case atom.Img:
+			default:
+				printWarn("Unknown data atom:", n.Data)
+			}
+			// Add some CSS effects.
+			if hasClass("spaced") {
+				// Add spaced effect.
+				var newRet string
+				var runes []rune = []rune(ret)
+				var nRunes = len(runes)
+				for i := 0; i < nRunes; i++ {
+					newRet += string(runes[i])
+					if i < nRunes-1 {
+						newRet += " "
+					}
+				}
+				ret = newRet
+			}
+		default:
+			printWarn("Unknown type:", n.Type)
+		}
+		return ret
+	}
+	for _, n := range content.Nodes {
+		fmt.Fprint(e.W, process(n))
+	}
+	return nil
+}
+
+func (e *Extractor) FetchAndProcessChapter(chapterUrl string) error {
+	// Get HTML document.
+	resp, err := http.Get(chapterUrl)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	// Parse HTML via Goquery (or really x/net/html).
+	doc, err := gq.NewDocumentFromReader(resp.Body)
+	if err != nil {
+		return err
+	}
+	// Parse page.
+	err = e.parseAdditionalPage(doc)
+	if err != nil {
+		return err
+	}
+	// Add horizontal rule after title page.
+	if path.Base(chapterUrl) == "titlepage.html" {
+		fmt.Fprintln(e.W, "----------------")
+	}
+	return nil
+}
+
+func main() {
+	var url string
+	dir := "."
+
+	if len(os.Args) < 2 {
+		usage(os.Args[0], 1)
+	}
+
+	// Parse command line arguments.
+	for i := 1; i < len(os.Args); i++ {
+		// Returns the argument after the given option. Errors if there is no
+		// argument.
+		expectArg := func(currArg string) string {
+			i++
+			if i >= len(os.Args) {
+				printErr("Expected argument after option '%v'", currArg)
+			}
+			return os.Args[i]
+		}
+
+		arg := os.Args[i]
+		if len(arg) >= 1 && arg[0] == '-' {
+			switch arg {
+			case "-dir":
+				dir = expectArg(arg)
+			case "--help", "-h":
+				usage(os.Args[0], 0)
+			default:
+				printErr("Unknown option: '%v'", arg)
+			}
+		} else {
+			if url == "" {
+				url = arg
+			} else {
+				printErr("Expected option, but got '%v'", arg)
+			}
+		}
+	}
+	if url == "" {
+		printInfo("Please specify a book URL")
+		os.Exit(1)
+	}
+	printInfo("Book URL: %v", url)
+
+	// Initial scraping.
+	var b bytes.Buffer
+	e, err := NewExtractor(url, &b)
+	if err != nil {
+		panic(err)
+	}
+	err = e.FetchAndProcessIndex()
+	if err != nil {
+		panic(err)
+	}
+	bookName := e.Meta.ToTitle()
+	printInfo("Book: %v", bookName)
+
+	// Download the actual chapters.
+	for i, chapter := range e.ChapterUrls {
+		fmt.Printf("\033[2K* Downloading chapter %v/%v...\r", i+1, len(e.ChapterUrls))
+		err = e.FetchAndProcessChapter(chapter)
+		if err != nil {
+			panic(err)
+		}
+	}
+
+	// Write the generated markdown text to a file.
+	filename := path.Join(dir, bookName + ".md")
+	os.WriteFile(filename, b.Bytes(), 0666)
+	printInfo("Saved as: %v", filename)
+}