My favorite on the iPad is probably Osmos. It comes with it. Google Earth is very good, too. I have downloaded a few free books, but haven't tried reading them yet.
You might end up looking at a different browser than Safari. Safari just up and quits for me every few days if I have 9 sites (the max) loaded. I've played a little with Atomic Lite and with iCabMobile. They each have issues - I haven't made the jump yet. Serious web browsing on the iPad v1 is still pretty immature, IMO.
It's still an amazing box, though. Enjoy!
Cheers,
Scott.