Here's some of the books I have found very useful since starting knitting.
We'll start with Knitty Gritty. This book is for the absolute beginner so it is perfect if you're just starting out. However I would say that if you just want to knit for Blythe I wouldn't bother with the projects in this book as they are rather time consuming.
Next is the Ultimate Knitting Bible. If you become a crazy obsessed knitter like me then there is nothing better than browsing through this delicious book. The pictures are lovely, the instructions are clear & easy to follow. In short this is Knitting Nirvana. It takes you through LOTS of knitting techniques rather than going through knitting projects so it's very helpful.
Onto Knitspeak, a handy little tome that lives in my knitting bag. This book is an A-Z of knitting language and abbreviations. It has helped me solve many a knitting puzzle.
And now Knit Aid another handy little book that lives in my knitting book. Despite being aimed at an American audience it is very helpful, with diagrams of techniques, helpful hints and problem solving.
And last but not least one of my favourites How to Knit. This is actually a kids book but I have found it really useful as the diagrams are easy and unlike Knitty Gritty the projects are smaller so much easier to finish.