I find it hard to believe there are people who have no clue what the book is about. Still the possibility exists so I will give the high points of the plot. See there once was a hobbit (a race entirely created by Tolkien and endlessly recycled since under name halflings - for copyright reasons) named Bilbo Baggins. Think a humanoid creature of about half of a grown-up adult human height with furry legs who goes barefoot - it is a hobbit.
These guys live underground in holes similar to rabbit's, but much more comfortable. Speaking about comfort, they love it and for this reason never ever go adventuring.
One fine day Bilbo was sitting outside minding his own business when Gandalf showed up. Gandalf was a wizard who gave birth to practically all mighty wizards appearing in any art form. Albus Dumbledore from Harry Potter is probably the most famous example and yes, he would not exist without Gandalf.
Anyhow, for reasons entirely unclear through the whole book Gandalf decided to involve poor hobbit into a grand adventure - the kind where heroes go from a mortal danger to being miserable from hunger and weather having just escaped said danger and to yet another mortal danger again, still remaining miserable. Who would not want it? By the way, this never-explain-your-reasons-and-motivations thingy is a trademark of all mighty wizards that come after Gandalf.
And so off to a grand adventure Bilbo went, accompanied by 12 dwarves and Gandalf himself who kept them company only part way. Adventure they wanted, and adventure they got, full of misery and dangers.
I said it before and I will say it again at the risk of making some people very angry: this is a children tale; nothing more, nothing less. If you are trying to find some deep philosophical meaning in it, you are wrong: it is not supposed to have any. You might as well find some hidden messages in Itsy Bitsy Spider.
Just look at Gandalf: the guy who dueled Balrog in the Lord of the Rings (this is an adult tale) at times looks like a total fraud in Hobbit: at one time he was sitting in a tree throwing flaming pine cones at wargs and set the forest on fire - his own tree included. As I said, a simple tale.
It does not make the book bad by any means. It is a children classic for children and adults alike for a reason. I had a blast reading it in my childhood; I reread it later and liked it and I still like it after my latest reread. The rating is 4 very solid stars.