I've read both the Arvind Nagpal and Rajeev Kasturi books, and I conclude that the Nagpal book is much better for me, a person who has been doing SAP EDI for several years.
I do not know either of these authors. I do not have anything to do with the publishers. I bet this is more than many of the reviewers here can say!
I know that sheer bulk is not what we are buying here, but let's do some numbers to examine one aspect of the comparison. The Kasturi book starts with 388 pages. Well over 100 pages in the back are tables out of SAP that we can print any time we want (or save a tree and just pull up a screen). Since I've worked with SAP EDI for a few years, I didn't expect a lot of things to be new to me in the first 3 or 4 chapters, but man, there was nothing even moderatly interesting to me in the early part of the book. That left about 150 pages in the middle that, I'll admit, I only skimmed. But the per-page cost of those few possibly valuable pages is quite high! There was a strong ALE / example flavor to the book. As if someone wrote about a few of their favorite implementations.
Now, the Nagpal book starts with quite a few more pages (786). There is NOT a huge section of this book dedicated to stuff I could print out of or look up in SAP. Yes, some of this stuff is 'light' too. And again, I'll admit to skimming a lot of it that I didn't have a pressing need to know right now. And yes, there are quite a few print-screens in the book (but I LIKE print-screens). The bottom line is that I, a person who's been using SAP-EDI quite a while, found the Nagpal title MORE INTERESTING, INFORMATIVE, and found it had MORE INFORMATION than the Kasturi book.
--Dale--