Heinlein's Juveniles is a 9-book series first released in 1948 with contributions by Robert A. Heinlein, Antonio Bonano, and 3 others.
1957 • 1 Reader • 350 pages • 3
1950 • 1 Reader • 193 pages • 4
1950 • 32 Readers • 207 pages • 3.4
1958 • 2 Readers • 276 pages • 3
1963 • 1 Reader • 166 pages • 3
1948 • 20 Readers • 224 pages • 3.2
1953 • 28 Readers • 284 pages • 3.4
1959 • 466 Readers • 353 pages • 3.7
1958 • 1 Reader • 317 pages • 3