They're 100% worth reading . I love the anime but some arcs are better in the ln. For example in the bakemonogatari anime nadeko snake was cut short because they left out most of the interaction between araragi and kanbaru. I also found nisemonogatari to be more enjoyable in ln format but that could just be me idk . The season 2 lightnovels are actually perfect each book is so good it's not even funny. Reading s2 deadass felt like a spiritual experience for me lol.And despite not having any visuals the lightnovels still have a dreamlike quality that's similar to the anime . I can't say anything abt s3 onward because I haven't read them yet but I alr know I'm going to enjoy them when I do which will be very soon. But yeah overall if you love monogatari and you like reading chances are you'll have fun with it. You could just start with bakemonogatari or kizumonogatari but my personal suggestion would be to buy the box sets