The Culture series is good but I've struggled with getting through it all as well. If you like space opera I can highly recommend the Honor Harrington series, the first book being On Basilisk Station [0]. This has held up for me for well over a decade and I've reread the entire series (~14 books IIRC) at least 4-5 times. I've heard it described as "Horatio Hornblower in space" but I never read that series so I can't speak to that.
[0] https://www.goodreads.com/book/show/35921.On_Basilisk_Statio...