I had a slightly different reaction; I felt that the author consistently treated Heinlein's and Ginny's memories as authoritative and failed to research possible contradictions. For instance, there is a case where* the author notes that Heinlein's files include a letter to his hometown library asking for some research to be done on the date that his family moved there, and the library's explaining that they weren't funded to do research, but they would suggest scanning the city directories of the time. The author reports this letter, but didn't bother to go to the hometown (or hire a hungry grad student) to do the research the library suggested.

But yes, way to not do history.

* synopsis from memory