Robert Caro’s next book isn’t his fifth and final volume on Lyndon Johnson or like anything he has done before.

“Working: Researching, Interviewing, Writing,” to be published by Alfred A. Knopf in April, combines personal reflections and professional guidance as Caro looks back on his singular history as a writer and reporter. The book includes previous lectures and interviews, but also new material. In the introduction, the 83-year-old Caro writes that the 240-page “Working” is not a “full-length memoir,” which he still hopes to write, but a more informal gathering of “thoughts” and “experiences” behind such prize-winning books as his Johnson biography “Master of the Senate” and his classic book on municipal builder Robert Moses, “The Power Broker.”