add readme, show help w/o args

README.md

@@ -0,0 +1,27 @@
+# epuppy - terminal epub reader
+
+This is a little TUI epub ebook reader. This is a work in progress and
+may not work for all EPUB files yet. It uses a modified version of the
+[epub module](https://github.com/kapmahc/epub/), which seems to be
+unmaintained but the best I could find to parse EPUBs. Find it in the
+`pkg/epub/` directory.
+
+## Installation
+
+### Installation from source
+
+Check out the repository and execute `go build`, then copy the
+compiled binary to your `$PATH`.
+
+# Report bugs
+
+[Please open an issue](https://github.com/TLINDEN/gfn/issues). Thanks!
+
+# License
+
+This work is licensed under the terms of the General Public Licens
+version 3.
+
+# Author
+
+Copyleft (c) 2024 Thomas von Dein

cmd/config.go

@@ -99,6 +99,9 @@ func InitConfig(output io.Writer) (*Config, error) {
 	// arg is the epub file
 	if len(flagset.Args()) > 0 {
 		conf.Document = flagset.Args()[0]
+	} else {
+		flagset.Usage()
+		os.Exit(1)
 	}
 
 	if conf.Debug {