The sentence you are referring to is a play on words - puns in any language are difficult for non-native speakers.
The real sentence is "his bark is worse than his bite." This means that "he makes a lot of threats but does not follow through," a reference to a dog that barks a lot but does not really bite.
In this particular case, Horatio Hornblower is a Royal Naval Officer in a series of novels by C.S. Forester. "Barque" is a type of vessel (ship), and "bight" is a type of knot, and sailors are known to tie all sorts of knots in order to secure their ships. So the one-sentence book report is a very clever play on the idiom "his bark is worse than his bite" and the nautical terms "barque" and "bight."
As a protagonist, Hornblower is also a reserved, self-doubting character despite his extraordinary skills. Therefore, saying that his "bark (barque) is worse than his bite (bight)" may be a good summary of this fictitious character.
I hope this was helpful.