Yes, Powell's books is quite a place. It is a multifloor maze of a bookstore. Check it out of you like books. Another place that Cloak didn't mention is the Portland Rose Test Garden. I was there a week ago and all the flowers were in beautiful bloom. You might just make it to see them in bloom. Plus up there you get a great view of the City.
If you are looking for a good city to explore I would recommend Portland much more than Clackamas.