Is it normal i didn’t understand the lord of the rings books when i first read them?

I read LOTR for the first time at about the same age as you did, which is now about 50 years ago. I'm sure there were lots of things I didn't get on that first pass. I read the three battered paperbacks I'd been given by a hippy uncle a couple more times before I moved on to other things, and I have fond memories of the experience of being immersed in the world of the Middle Earth. In fact, the books played an important role in my life since they created a desire to visit Britain. That led to me coming here in the mid-seventies, and I basically never returning to the USA where I was born and grew up.

I've tried to reread the LOTR a few times as an adult, but I've never been able to get into it. The biggest problem for me is Tolkien's use of English, which I find stilted and pretentious.

Hemingway and Tolkien were born just a few years apart and they were writing at the same time, and yet Hemingway is still easily readable, while Tolkien comes across as a 19th century author who wrote in a deliberately archaic and convoluted style in an attempt to sound like a medieval tale such as Malory's Morte d'Arthur. The text being challenging to plough through creates a barrier to the suspension of disbelief that fiction requires, and I can't get past the feeling that the whole story is fake and irrelevant.

You're right about Tolkien's main concern being world-building. He was an academic with an obsessive interest in ancient languages who had personal experience of the hell of the First World War trenches and the Battle of the Somme, and a devout Roman Catholic with socially conservative views who lived in a period of great technological and social upheaval, including WWII. Although he was adamant that the LOTR wasn't an allegory of any sort, it's clear that the times he lived in and his dislike of the changes he saw going on around him are reflected in the story. The LOTR has a huge cast of characters, but many are sketchily portrayed, and they all are all no more than puppets with archetypal personalities and motivations who he moves through a world that's in the midst of a cataclysmic battle between Good and Evil. The tale is further slowed down by Tolkien's inability to resist the temptation to stuff in ancient backstory, irrelevant characters, snippets of the languages he'd invented and poetry.

The Hobbit was always intended to be a children's book, while the LOTR was written with a more mature audience in mind. Rowling's Potter books (which I dislike for being derivative and stocked with characters as shallow as Tolkien's) were also aimed at a young audience.

There's no requirement that you like the LOTR any more than you are required to enjoy reading Shakespeare, Tolstoy or Hemingway. Some people find the work of Tolkien pleasurable to read and as profoundly meaningful as those other authors, while others dislike the work of one or another or all of those writers. About all you can truly say about all of them is that they are significant figures in the history of literature, they all have had some influence on the writers that came after them, and so therefore they have had an impact on modern culture and society.

By the way, any LOTR pedant would be quick to point out that the book is not a trilogy. Tolkien viewed the work as a single "heroic romance" (meaning that in the classic, medieval sense, which is very different to the modern meaning of "romance"). It was originally published as a set of three books because of the limitations of printing technology in the 1950s and because the publisher believed it wouldn't sell well. The Fellowship of the Ring was basically a trial run, and when it sold enough copies to recover printing costs, the other two books were published.

Finally, I have to say that I think it's always a bad idea to read prefaces first. Most often, they're pretentious twaddle written by some pompous ass who's desperate to show off their profound understanding of the deeply meaningful themes of the work. Prefaces are always at the front of the book, but they should be read last - if they're read at all. Read the book and experience it for what it is, then check out the preface if you feel the need for another take on it, of if you're left with a WTF feeling.

I was about 13 when I read the trilogy, and didn't like it. I don't think I ever finished the third book.