What other readers are there in your social circles? Many people find it easier to read if doing yields social rewards.

Example: I want to improve my ability to write with a richer vocabulary so therefore I should probably find the best English classics and authors known for their vocabulary (Shakespeare, Joyce..). What are 1-2 books by each of them? Read them -- learn with intention -- and it will not feel like a chore that requires you to "stay motivated" and you'll just do it.

You could easily read a self-help book in a day. A classic might take you a month. A textbook probably a couple of months. Speaking from experience, focus less on the number and finding quality things consume that will teach you something meaningful and long-lasting.

So you create a small Todo list and on that list you have something like -

Read x amount of pages of a book.

Do X

Do X

Go to the Gym

Etc. Etc.

Everyday you wake up and try to complete the activities on the list.

Slow and steady. Consistency over intensity.

You'll see that the number of pages you've read will add up very quickly. Just keep it manageable. It's not a competition.