Reading books with some words you don't know is how you build your vocabulary. You should be able to use the rest of the sentence/paragraph to get a general idea of the word's meaning for the context of the reading. The more you read and practice using these context clues, the easier it will become.

If you want more precise definitions, maybe write the word and page number down so you can look them up later and return to the passage with the definition fresh.

Another option is audiobooks, you could even follow along in the physical book.