My son loves to read. He has a library at home larger than that of his classroom, and he is always asking to add to it. For Christmas Santa brought him the first 43 books books in the Magic Tree House series (we had already read 5 or 6, but he was super excited to have them all), along with 3 Skippyjon Jones books, and a few others as well. We also did 25 days of books at our house for Christmas, where every night, Elliott got to open a new book that I had wrapped up, and then he read that one to us, as well as a Christmas book or two. It was a big hit, and we all really enjoyed it. He ended up with even more books on Christmas from us as, and a set of 3 from an aunt, for a total of about 90 all together for Christmas.
Because he loves to read so much, finding books he will like is relatively easy. However, finding books that are age appropriate, as well as challenging can be a little more difficult. He's only in first grade (he will be 7 next week) but already reads on an upper fifth grade level. He loves everything from easy picture books, to chapter books.
We never check out regular chapter books from the library anymore, because it seems like every time we do, something comes up, and we are unable to finish them before they need to go back. However, we love checking out picture books and early chapter books from the library. We also look for great deals on them used, or through Scholastic book club, so we can continue to build his library with books that he will actually read over and over, or that I am fairly certain a future younger brother, sister, or cousin will enjoy as well.
I think that one key to encouraging his love for reading is to give him a wide variety of books. His bookshelves include everything from classic favorites from his early days (Berenstain Bears, Clifford, Dr. Seuss, Curious George, etc) to books that are popular for first graders at his school right now (Fly Guy, Skippyjon Jones, Mr. Men and Little Miss, Henry and Mudge, etc) to easy chapter books (Magic Tree House, Magic School Bus, Black Lagoon chapter books, My Weird School) to regular chapter books (Harry Potter series, Narnia series, Little House on the Prairie books, Barbara Robinson's Best __ Ever books, Charlotte's Web, etc).
We also have books on several levels about Super Heroes, Legos, Sharks, Snakes and Dinosaurs. He doesn't care if the book was designed for a preschooler or a fifth grader, if it's about one of those subjects he WILL read it.
We also make it a point to make time to read to him, and listen to him read frequently. We make sure that we have time at least 5 days a week. It's a priority, but not something that we can always do everyday, so we give ourselves a little wiggle room for when things are too crazy. I would say we average missing just 2-3 days a month, though. We let him pick what he reads to us, and what we read to him, too, with the only stipulations being that at least one chapter of at least one book be read every day, and that we don't have more than 5 chapter books going at any one time. Right now our chapter books include a Magic Tree House book, a Hank the Cowdog book, a Star Wars chapter book, and a book all about Marvel Comics.
I also make it a point to show him how much I like to read. Although we rarely actually buy books from Barnes and Noble, we do frequently browse for books there, and Elliott gets ideas for books that he wants to look for online, at yard sales, or at the libary. He also likes to help me pick books that I might like while we are shopping, and then he gets excited if I end up borrowing it from the library, or getting it on my Kindle.
Reading is so much fun when we do it together!