Each volume is about 1,000 pages of small print. They're all incredibly interesting, but still slow reading. My strategy has been to borrow the book from the library. The loan period is 3 weeks plus one renewal. I usually can't get through the entire volume in 6 weeks, so I return it as I need a break. This is when I read a few mystery novels. Then I borrow the Johnson book again and finish it.
The Kennedy/Johnson campaign in 1960 is the first presidential election I really followed. I was in high school when Kennedy was assassinated and Johnson became president. This 4th volume that covers 1960-1964 includes incidents I remember.
The entire series has been nothing short of fascinating which is why I've persisted through 4 massive books. Robert Caro writes in amazing detail, but his writing is never boring. It is vivid and engrossing. Reading any part of the Johnson story, I can practically feel myself in the situation: what life was like in the Texas hill country during the Depression; why the U.S. Senate works the way it does (it was designed to be "thoughtful" i.e.slow and plodding). I've learned so many things.
I strongly recommend these books to everyone, even those not interested in American history or government, though reading them is definitely a commitment.