The book is short (150 pages), and nothing like as dense as it thinks it is (unless you're not used to tonnes of anonymous functions and lexical closures). This book has made me decide I prefer BNF to railroad diagrams. It's chock-full of railroad diagrams. The best book to compare it with, given the similarity of coverage, is Programming in Lua. I'm afraid the comparison is not favourable. The Lua book is rather longer, but does cover so much more (including all the business with C bindings), and is so much more pleasant and fun to read. It does, of course, have the advantage of being written about a coherent and sensible language.