This book is like a slap on my face about all the failed negotiating I‘ve done in the past.

Very good advices to any type of negotiations, including outside business environment.

very very helping for neplo

Having read this over 20 years ago, it bears re-reading. Method is solid, and reading through the detailed table of contents (and occasionally dipping in to re-read a passage) should keep things fresh.
Not the easiest book to read, but does have enough examples to help illustrate most points.