OS/2 API Research book, written in Russian (cyrillic), had been updated (2014/04)
http://hobbes.nmsu.edu/h-search.php?key=os2book
This is the complete reference and tutorial for Control Program and Presentation Manager programming. Alongside with CP/PM API calls, this book describes modern API calls (eToolkit, LANGE, libKVA) and low-level DDK Helper functions. Based on that, it shows possible roadmap of OS/2 development towards functional programming and mikrokernel architecture.
By: Sergey Posokhov