I enjoyed all the books, although I can understand why some people say that it drags in parts. There are a lot of parts of the book which are basically various characters travelling a long distance. They walk over hills and lots of description of landscape, then they eat supper and sleep. Then they get up and walk again with more description of landscape and then sleep. I guess Tolkien wants to give a feeling of the length of the journey which you wouldn't get if he just said "and then they walked for six days until they got to..." but it does drag.
Still, it was ok, I never got so bored that I lost interest in the plot, as enough happened to keep it going.
I think the first book is the best, especially the first half. There is a sense of looming danger and foreboding with the whole learning about the ring and Sauron, the sense that the ring bearer is now hunted, the entry of the ringwraiths, that is absolutely captivating. The rest of the books are good but maybe after the breaking of the fellowship it feels a bit different. There are a lot of other sub-plots that feel more standard in nature, this group fights that group and so on, and it takes away some of the foreboding of it.
Also I felt like the ending seemed to resolve itself a bit too easily to be honest. For much of the third book, the main characters seem to have accepted the hopelessness of their situation and are just fighting gamely till the end because there's nothing else to do. But then whenever there is a major battle it seems that the enemies aren't as formidable as they are built up to be. The orcs turn out to be bumbling fools and Sauron isn't as omnipotent as he's made out to be. Even the wraiths turn out to be a bit of a let down, including the Witch King. To some extent the biggest threats come from outside dangers like Barrow Wights, the Balrog and Shelob.
It feels a bit like Tolkein built up this formidable enemy and then realised he had to bring the book to an end so gave the good guys a load of rapid victories to bring the war to an end, and then just to show it wasn't all too easy he throws in the last battle at the Shire.