I've had this in my Amazon wishlist for a few months now.
How does it compare to I, Claudius?
I did not read I, Claudius so I can't compare.
The book it's a letter that dying Hadrian it's sending to his young heir, Marcus Aurelius, retelling moments of his life, so it's written in first person. It's not dynamic or exciting but it is well written and it is immersing because it feels like it was written by him. I probably like it because I find the character of Hadrian fascinating even with his flaws; the passionate traveler, builder and efficient administrator, stoic and compassionate, that loved peace, greek culture and a bythnian boy it's very different from usual depictions of roman emperors that are either statue-like heroic generals and statesman or caricature-like cruel monsters.
The period it's also fascinating with greek and roman traditional cultures at their peak.