I'd recommend (before or after license doesn't matter)
- Shawn Coyle's "Cyclic&Collective" and "Little book of autorotations"
- Greg Whyte's "Fatal traps for helicopter pilots"
For some more aerodynamical insights:
- Ray Prouty's "Helicopter Aerodynamics" (a 2 volume collection of his articles)
By the way, the FAA "Rotorcraft Flying Handbook" is freely available at
https://www.faa.gov/regulations_poli...uals/aircraft/ as a pdf.
Keep in mind, that the new version is called "Helicopter Flying Handbook" which is also available at
https://www.faa.gov/regulations_poli...ying_handbook/ as seperate pdfs per chapter or as one big pdf.
On these pages you'll also find many more interesting stuff (not only, but partly also rotorcraft related).
Have fun
Thracian