For the last half-century, the writer Robert Caro has been churning out a series of books about Lyndon Johnson.

Well, maybe “churning out” is an overstatement — Caro has been producing a new book in the series, “The Years of Lyndon Johnson,” every decade or so since the first volume, “The Path to Power,” in 1982.

The series now includes four books, totaling some 3,000 pages.

And Caro isn’t done: At age 89, he’s still working on the fifth and final volume, which will cover the last years of Johnson’s presidency.

I can hear you now: After 3,000 pages, the series hasn’t gone past 1964?

That’s right. But Caro, a tireless researcher, has gathered so much detail about Johnson that the books have a page-turning intensity that belies their length.

Part of this is thanks to Caro’s skill. And part of it is due to Johnson’s bigger-than-life personality.

Caro doesn’t try to hide Johnson’s flaws: By many measures, this was a despicable man, racist, vulgar, manipulative, skilled at finding the weaknesses in other people and exploiting them. But Johnson also was key in launching the nation’s war on poverty and the Great Society, which brought us Medicaid and Medicare. Caro carefully examines the abundant contradictions in Johnson’s character.

The best book in the series might be the fourth, “The Passage of Power,” thanks to its relatively tight focus from 1958 to 1964, and its riveting description of the day John F. Kennedy was assassinated and the following weeks. It also brings to life one of the great political blood feuds of the 20th century, between Johnson and Robert F. Kennedy.

When it’s finished, “The Years of Lyndon Johnson” will stand as an unprecedented document of a president’s life and times, and a peerless examination of the uses — and abuses — of political power.