i would look at a few that are 1 page long prelude and 1 page long fugue. i just finished a few from book 1 and g sharp minor p and f from book II. Let me tell you, after working on multiple p&fs at a time, I now sight read some of both preludes and fugues. When working on a fugue, if you can't read a part of it, try taking just one or two voices in one hand, then add voices one by one, until you are playing all voices together. I am a drama queen, and I love the minor fugues, such as the c sharp minor (this fugue is more beautiful when played from the heart/memory, as it is lament, a complaint, a sad prayer) book 1, the f minor, the f sharp minor (OMG, I recommend! read it.) g minor (g major is exciting, the fugue is very nice), g sharp minor, a minor (VERY TRICKY, I do not recommend!!!), b flat minor...
some of the beautiful ones, an easy one is f sharp major, if you can do the trills. it is so gorgeous, A major is the most beautiful prelude. E flat major is amazing to learn, as well...the e major prelude is 1 page and so is the fugue. It was very fast to learn, and the fugue is very exciting.
i think i listed 12 of 24 from book 1. that's a start on book 1.