I read the first three volumes and at least attempted all of the exercises. I got the easy ones, made some progress on the harder ones, and at least understood

I read the first three volumes and at least attempted all of the exercises. I got the easy ones, made some progress on the harder ones, and at least understood the "impossible" ones. These books are written on the assumption that you're going to work all of the exercises - I don't think that if you just read them you'll get a lot out of them. I really enjoyed working through them - I keep meaning to get around to volume 4, but can't seem to find the time to do so.