competent rather than stunning, inclusive rather than unified, -- and written, most probably, under the simple rubric, 'a book about books has to get some
readers, engineer Henry Petroski can write, but doesn't stun or immediately derive a rabid following. much of the book is concerned with bookshelf designs, and while three or four pictures of medieval bookshelf concepts (a rotary concept, an angled lectern) are fine, by the thirteenth or fourteenth, you're wondering of the writer needed to produce filler.
Petroski missed the opportunity to track a book from production to finish (he could have covered papermaking, ink production, tree farming) and he could have researched unusual or extreme short production books (Evelyn Waugh did a leather edition of 200 for his close friends of Brideshead Revisited; there was a medieval book with iron covers called Malleus Witchitorium or something like that, 'hammer of witches' which was designed both for reading and to be physically used to beat witches to death--I'm not making this up). if I know these two random facts about books, then Petroski's lack of deep research is clear since he probably could have come up with 100 totally unique books or publications with a little more willingness to talk to librarians or allied professionals.
a competent, not-horrible 3.