I purchased this when it was a free promotion, but it's definitely worth paying for, for two reasons.
First, the pictures are delightful! We read this on a Kindle Fire, which I'd guess is the best way to read it on a Kindle device. I can't imagine it without full color; the detailed illustrations wouldn't be nearly as lovely in black & white. I especially loved the subtle humor in the "K is for Kiwi" page, although it will be a while until my 2yo gets the joke.
Second, I can see this being a good read for babies all the way up to preK kids. The "__ is for _____" text is very simple, probably best for the under-3 crowd if read as-is. With a bit of extra discussion, though, it's entirely appropriate for older little ones, too. For example, "W is for Watermelon. Where is the watermelon? What color is the watermelon? Is the watermelon big or small? Would watermelon taste good in soup? What would YOU put in a watermelon soup?" and so on. Just by casually talking about the pictures, you could cover color, counting, size, food groups, nutrition, and plants/growing things. Not all at once, of course, but through repeated readings, which many younger kids enjoy if you do it right. I know mine love it, and my 2yo has asked to read this again quite a few times.
If you're looking for an ABC book for your toddler or preschooler, one that has great pictures AND great re-read value, Dragon's Alphabet Soup definitely fits the bill!