Hi Satya,
There are two possible reasons( I guess) why sap press didn't have material for TPM.
1-The consultants who had the knowledge/experience doesn't want to write a sap-press book
2-There isn't enough knowledge in the market to write a decent sap-press book, when I mean enough knowledge I mean, projects focused in use SAP TPM with its "full potential" .
Right now the only tree sources for TPM is the SAP library:
Trade Promotion Management - SAP Library
The offical SAP course ICP600:
ICP600 - SAP Trade Promotion Management | SAP Training and Certification Shop
Notes and KBAs
You can also ask for links-Blogs in the marketing section
Cheers!
Luis