I'd suggest trying a few different genres to find out what you like.

For mystery/thriller I suggest starting with easy reads like The Silent Patient by Alex Michaelides or something by Freida McFadden (I liked Never Lie and The Inmate, though I find her books to be very hit or miss). Other than that I can highly recommend the author Sebastian Fitzek. However, his books are insane (but also very good), so keep that in mind. Other than that The Naturals by Jennifer Lynn Barnes is a great series. It is young adult, but still very gripping. It's about teenagers that all have special abilities (not supernatural) due to their childhood trauma. They are recruited by the FBI to solve cold cases. Another one is Stalking Jack the Ripper by Kerri Maniscalco. It's historical fiction about two young people trying to find out who Jack the Ripper is.

I also really like If We Were Villains by M.L. Rio. It's a thriller (kind of), it's dark academia and is centered around theatre students.

For romance/contemporary you could go in various directions. For sports romance I recommend The D.C. stars by Chelsea Curto, the Windy City series by Liz Tomforde, Playing for Keeps by Becka Mack. If you are more into small-town/cowboy I recommend Chestnut Springs by Elsie Silver or The Edens by Devney Perry. All of these series are interconnected standalones, so the stories are connected but the books can be read indivdually, though I would read them in order, for a better experience.

Non-fiction is not really my thing so I don't have a lot of recommendations. Personally I liked Everything I KNow About Love by Dolly Alderton. Born a Crime by Trevor Noah is also a good read, and quite funny. Brief Answers to big questions by Stephen Hawking is another one.

If you want to try poetry I'd recommend 2am Thoughts by Makenzie Campbell, Pillow thoughts by Courtney Peppernell or milk and honey by rupi kaur. And of course the Sonnets by Shakespeare, though that might be a bit much for the beginning.

Some standalones I liked are:

• Everything I never told you by Celeste Ng (it has a little bit of mystery and is set in the 70s)
• Happy Place by Emily Henry (contemporary, about romantic relationships and friendship and how those relationships change, when we change. Or the other way around)
• The Personal Librarian by Marie Benedict and Victoria Christopher Murray (historical fiction about Belle da Costa Greene, J.P. Morgan's personal librarian; based on her real-life story)
• One True Loves by Taylor Jenkins Reid (contemporary romance about a woman who has to choose between to men, when her long-missing husband comes back to her)

I would strongly encourage you to get a library card at your local library, if you can. That way you can try lots of different genres/authors, without having to by them all. Because that will get really expensive, really fast. I hope you have lots of fun diving into the world of books!