If you're planning to read 26 books in a year it might be advisable not to start with one that's more than 800 pages long. That's what I did and it took me all of January to finish it. Underworld is considered one of the classics of the 20th century and I can see why - the writing is superb and there are some astonishing scenes. Unfortunately the book often feels like little more than a collection of set pieces.
This Wikipedia entry explains the plot, such as it is, but the story isn't really important. It's not a book that has you racing to find out what happens next and I have to admit I was beginning to lose interest by the time I reached the end.
Another problem is that pretty much every character speaks with DeLillo's distinctive voice, elliptical, declamatory, pedantic - even the kids. And almost every character shares the device of carrying on two or three conversational threads at once - hard to follow at first but eventually it becomes quite an enjoyable rhythm. Still, those tics hurt the authenticity of the characters - they feel like creations rather than people.
Nevertheless, DeLillo does a very good job of showing how a trivial thing, such as a baseball, can have an enormous effect on a life, and how major political forces, the Cold War, for example, can affect us all, often in the tiniest of ways. It's an extraordinary achievement.
If you're a patient reader and you're happy to follow meandering characters rather than get immersed in a plot, you'll enjoy Underworld. Anyone who enjoys good writing should read the big set pieces - the opening baseball game, the highway shooting, the Zapruder film and the Lenny Bruce sets - but it can be slow-going in between and Underworld might just try your patience.
I'm glad I read it. But I'm glad I don't have to read it again.