Should have been written a long time ago,
This review is from: Official ABAP Programming Guidelines (Hardcover)
ABAP is a very odd programming language. Based on COBOL with lots of other influences it's essentially only used in SAP AG's ERP technology. The problem with ABAP is that it's pretty much only taught by SAP and by their own books and example code.
An awful lot of ABAP written by SAP on their courses and within their products is dreadful. It's written to work and not to be supported/maintained. It's is riddled with spaghetti code, bad and shameful practices and terrible short cuts.
Much ABAP code is "cut and paste" coding with no thought for the future and that gets the job done today but puts the cost off to tomorrow. This is a common problem with all languages not just ABAP, but unlike more popular or open languages ABAP is a bit trapped in it's own ecosystem.
This book is the best practices, coding principles or patterns book that every other language has had for a number of years. The principle behind the book is to take all the good ideas or patterns that ABAP coders use and all the "official" ways to use the language ideas and fuse them into one long list of "dos" and "don'ts". The plan being that the code you write with this books will be readable to any ABAP programmer who looks at it but also it won't become a maintenance nightmare for someone else in the future.
It's not an exciting read but it's a list of good ideas and the rational behind them. Every SAP ABAP team should have a copy of this book and follow most of the ideas in this book. You should never follow a list slavishly but it is a really good place to start your journey from.