The Knitter's Companion by Vicki Square is a very helpful reference book. I also have Sweater Design in Plain English by Maggie Righetti, which has lots of good information in it. Modern Top-Down Knitting by Kristina McGowan isn't the best top-down book you can get (her ideas of shaping using non-knitting techniques certainly leaves something to be desired), nor are the patterns all that great (in my opinion). However, her explanation of how to pick up and knit sleeves in top-down constructions is worthwhile.
I understand that anything by Elizabeth Zimmerman is worth having even though I sadly have nothing of hers.
Do some searches on Amazon and read some of their reviews. You'll get opinions galore and references to plenty of other knitting books, too. Have fun looking!
You know, I didn't even think about going to my library! I'll have to make a trip tomorrow and see what they have. The best part about that is that those books are free, which leaves me more money for yarn!
When I first started, I picked a project I liked and just worked it through line by line. Some websites like Lionbrandyarn.com have free patterns which are categorized by your ability: beginner, intermediate, and advanced. If you don't know an abbreviation or a technique, you can ask someone here in this forum. You can also learn how to make Youtube your new best friend. Youtube has videos on how to do almost everything. For an old dog, I'm still learning new knitting tricks from Youtube. KH also has great instructional videos. Another good pattern site to go to is knittingpatterncentral.com. Why pay for a book when you can get patterns for free? I found that when I did buy books, I only used a few patterns. Most of those books have an introductory section on knitting basics that most knitters don't need to read anyway. And don't forget Amazon's Kindle or Barnes and Noble's Nook e readers. You don't need to have one of their units. You can download Kindle or Nook for your computer or laptop from their sites for free. You can then order all kinds of e knitting books from their sites and not need any space on a bookshelf. Plus you get the ebook instantly.
Purchasing books can be a colossal waste of money. Here's what I do these days: go to Barnes and Noble...or the library...and spend hours pouring over all of the knitting books. Buy then and there, or look online to see if it can be obtained more reasonably priced.
I have a nice collection of books, but I've wasted some money on a few clunkers, too.
I have a few books, but honestly I find more patterns and tutorials online. If I really want a book I only buy those that have several patterns I'd be really interested in making. If its only one or two patterns I look at my library. I use the online library catalog so that I have choices throughout the system then I put it on hold and have it sent to my local library. This works for instructional books too.
When asking questions ALWAYS post the name and a link for the pattern if you have it.