So the skim spell says you read 4 times faster. I dont know of anyplace in the rules where an actual reading speed is ever listed.
The only place I can find anything is under linguistics
Varies. Deciphering a page of ordinary text takes 1 minute (10 consecutive rounds). Creating a forgery can take anywhere from 1 minute to 1d4 minutes per page. Detecting a forgery using Linguistics takes 1 round of examination per page.
Which is only helpful so far as it sets the high bar, but since its for something more complex than simple reading, you know regular reading must be able to go faster.
You could also consider the rules for spell preparation for a 20th level wizard. Their able to prepare all their spells (with 9th level spells needing 9 pages each for 184 pages) can read their 184 pages worth of spell notes and prepare their spells in an hour.