E.H.
I also read Healthy Sleep Habits, Happy Child and really liked it. It gives you plans for each stage of your child's development and tells you what is appropriate to expect at each age. With my son, this book has always been spot-on in describing what he was going through at each stage. My son is a great sleeper now and was sleeping through the night from an early age (I believe, thanks to the book. And when I say "sleeping through the night, this just means sleeping a 7 or 8 hour stretch at around 3-4 months).
I know in my case, I was so overwhelmed by the lack of sleep and exhaustion of being a new parent that I had no idea (or energy) how to come up with any plan to get my son to sleep better. The book helped me formulate a schedule and I really think that CONSISTENCY is the biggest key in getting your baby to sleep better. Come up with a plan that works for you (either using the book, or just on your own) and then just stick with it. After a week, you'll be amazed at the difference. I think at three months, it's still reasonable to expect to get up a couple of times a night for feedings, however, you can start feeding at regular intervals and gradually moving toward more predictable naps of longer duration.
Good luck - the first few months are SO hard, but you'll get through it!