I'd personally recommend Haskell Programming from first principles (haskellbook.com) if you decide to look into Haskell. I've been making my way through it and

I'd personally recommend Haskell Programming from first principles (haskellbook.com) if you decide to look into Haskell. I've been making my way through it and I really like the progression of topics, and the thoroughness of the exercises. Currently starting the Monads chapter, and I feel like I have a solid grasp on everything that's come before. Background: I took a programming languages course on the way to my CS degree, which included Standard ML. I found it very interesting, but didn't take it seriously afterwards. The book lets you start fresh from the ground up (the first chapter is on the lambda calculus iirc), and I've really enjoyed spending my time with it.