Due to pop culture (movies, shows, games, etc.) I learned English. I also picked up two other languages due to school and influences from vacations.

So I’m fluent in three languages (Dutch, German and English) and can speak enough French to manage on vacations.

I read most of my books in English because I like to read books in their original language. I read a lot of hard scifi, this is a pretty specific genre and there’s little books in Dutch hard scifi books.

In Dutch I read general novels with no specific genre.

I’ve tried to learn Spanish, and would love to get to that point, but I really wonder if I’d be able to enjoy reading for leisure in another language, or if it would feel like a chore.

It's a pain at first, don't get me wrong, but if you start with a decent amount of knowledge you should be fine. Definitely not something to do before you have confidence in your command of the language, though.

Source: Learning Japanese, been there.

I also mostly read books (or consume media in general) in English and I was not raised speaking English. I had English in school but most of my English skills come from watching movies/TV shows in English with subtitles in my language. After a while I switched subtitles to English too.

It was not easy to take the plunge, first few books were definitely harder to read but I got used to it after a time - it also really helps your English to consume the media in it. I see it as easier alternative to go living in English speaking country - by far not on par, but was good enough for me (I'd not say I'm fluent though)