For practical tips/strategies (some of these are repeats from other posters)
Becoming the Parent You Want to Be
by Davis & Keyser
Parenting with Purpose
by Lynda Madison
The Secret of Parenting
by Wolf
Positive Discipline: The First 3 years
by Nelson
Note that there's a fair range of techniques that fall under the umbrella of Gentle Discipline -- some are OK with rewards, some not. Some are OK with timeouts to cool down, some are not. Part of your journey is going to be to figure out what feels right to you and what your parenting philosophy is. (That's one of the reasons I like Parenting with Purpose -- it talks about how all the techniques in the world won't do you any good unless you know why you're doing what you're doing. At the same time, it advocates rewards for the over 4 crowd, which some people are strongly against. I found the book extremely helpful for the toddler stage.)
Good books for the 'mindset' or philosophy:
Playful Parenting
by Cohen -- this is one of my all time favorite books. It really helped me to understand and to value spending time with my kids. It's about much more than playing, it's about connecting with your kids through play. It's actually got a lot of practical tips, but they work better with the 3+ crowd, in my experience, so for you, this might be a foundational book.
Unconditional Parenting
by Kohn - this is a great book if you've already committed to a GD perspective are looking to take it one step further. His work is always thought provoking.
Raising our Children, Raising Ourselves
by Aldort -- this book is good, I think, for people who are really trying to understand the mindset and shift perspectives. If you've already shifted perspectives to a GD perspective, it can come across as patronizing/holier-than-thou, IMO. (But that may just be me.)
Connection Parenting
by Leo