The Hal Leonard Ukulele Method Book 1 is an excellent teaching book that teaches both strumming and playing tab (single notes played on individual strings), along with playing 12 bar blues and some more advanced techniques such as playing tremello. It also introduces you to how to read music, for those who've never learned. It goes at a good pace so you can work through it at your own speed with each lesson building on the previous so you move along. Okay so playing Twinkle Twinkle Little Star and the like may be a little boring at times, but they're nice easy tunes so you're not just playing repetative exercises all the time.
However I would not recommend this book for absolute novices who have never held a ukulele in their lives before now. I think it starts off a little too complicated. There are many other excellent books and websites out there to get you started. Once you've got going a little bit, maybe even to the point of learning a couple of easy songs, then this is absolutely the book to get you on and get you progressing further - especially if you want to learn to read music alongside chord charts, or if you want to move on to playing melodies on strings. This is definately the book to turn to to start turning yourself from a beginner to what I would want to call an intermediate player, where you're maybe attempting things slightly more complicated than 3 chord 4/4 timed easy tunes.