We earlier reported that there will be 270 perks in total. Bethesda has now clarified that it is 275 perks, but relax, you won’t have to deal with an inconceivably large number of perks to study, and they didn’t stuff it with filler either.
Instead, some of the perks have XP levels on their own. Every time you finish a level, you can choose to buy a new perk, or level up one of the perks you already earned. This adds to your total XP rank. If you remember buying and/or leveling up skills in Diablo 2, it’s exactly the same.