What is the best jumping on point for Punisher?
I assume you're asking cause your curious about the new ongoing? Each writers take seems to be largely self-contained. I'm not sure they ever explained how Castle escaped the undersea detention center after the Avengers caught him at the end of Rucka's War Zone mini-series wrap up to his main title. He just showed up in Thunderbolts, tied to a warehouse column.
I would read all of Rucka's 16 issue run + the War Zone 5-ish mini wrap up. The two-issue Trail of the Punisher was a good read as well by Marc Guggenheim, if brief. They should've just made it one prestige book for $7.99, felt kinda odd and standalone existing in a vacuum. Post War Zone mini and during Thunderbolts run where he's an ongoing team member. Taken as just a story it was a good read.
Edmonsdon's first issue, this week, was well done and has overtones of a more social Frank as seen in Mike Baron and Chuck Dixon's 90's run but still able to be violent as seen in Remender/Rucka run's but not slap stick silly as Ennis' 616 run was(his Max is another beast).
Get the new Punisher #1, issue #2 comes out in two weeks and issue #3 two weeks after that before going monthly. There is a somewhat surprising reveal at the end of issue #1. Someone(s) is trailing Frank, to what end and why?