Answer: 34 books
Explanation:
Since Erik read a total of 4 books over 2 months. This means that every month, he read (4/2) = 2 books.
After belonging to the book club for 17 months, the number of books that he'll have read will be the number of books he read per month multiplied by 17 months. This will be:
= 2 × 17
= 34 books