This is an unread paperback with an uncracked spine. It does have some signs of wear due to age but overall excellent condition.

"Tunnel Through Time" by Lester Del Rey.

Here's some information about the book:

Genre & Plot: It's a science fiction novel, specifically a children's time travel adventure. The story follows a teenager named Bob Miller and his friend Pete, who travel back in time to rescue Pete's father, a paleontologist who disappeared during a time travel experiment in the Mesozoic Era. Their journey involves navigating various prehistoric periods after their time machine is damaged.

Author: Although published under Lester Del Rey's name, the book was actually written by Paul W. Fairman.

Publication: The book was originally published in hardcover by Westminster Press in May 1966 and later in paperback by Scholastic Corporation. The specific paperback edition in your image appears to be a Scholastic Book Services print from 1967 or 1970, with the publisher's book number TX1065 clearly visible.

Significance: "Tunnel Through Time" was widely used in elementary and middle school classrooms and gained popularity for its straightforward and engaging writing style.