I get this question here and there and wanted to make it clear. Both Life with Toddlers and Toddler ABC Guide to Discipline have the same information - but Life with Toddlers just has much, much more! The ABC Guide is like the cliff notes to Life with Toddlers. I wrote ABC Guide because I was getting so many emails from people who clearly did not have time to read a 200+ page book (Life with Toddlers), and could benefit more from a very quick, nitty-gritty guide with no cutsie stories.
So if you are a book reader, get Life with Toddlers. It has about 228 pages of information, and more elaboration on the technique with several more toddler issues (sleeping, bottles, etc.) It also has a chapter on developmental skills - what they should be doing at what age - so you know if what you are asking and expecting them to do is a reasonable request. We mommies forever wonder "When is the right time to teach X, Y, Z?" This list will help!
If you have no time to read (or don't like reading), no idea where to start, possibly did not have a good example of parenting growing up, and want very basic, quick answers, get ABC Guide to Discipline. It's only 80 pages, and will give you a fast start on the right track.
Hope this helps! Good luck!