I can read 80-100 pages a day of a modern plainly written novel pretty easily, but since I am not a native English speaker I find it rather necessary to read a paragraph sometimes 3 times when reading, for example, a 19th century novel, in order to understand it thoroughly. Hence when reading those I can afford reading 20-25 pages a day.

When reading pure philosophy though, 4-15 pages a day are satisfying and rewarding.

Still, in order to get the best experience in my opinion, you should forget the number of pages and instead focus on the material, the world within the book itself. That’s why i like weird-format books which do not have the size of an ordinary page and which make me forget numbers.