Of all the crochet books i've seen, i would definately recommend this one! This book was so helpful! there are pages and pages of crochet stitches - each with sample images, patterns and easy to follow instructions. The book also has an intro to show all the different stitches so if you get stuck doing one pattern, you can refer back to the intro. Also has a selection of crochet trims to learn and instruction on how to change colour yarn etc. Great book!! Didn't think i could ever learn how to crochet, but I've done it!
I'm not sure how helpful this is to a more advanced knitter but there are many fantastic stitches and a great reference book.