The main problem with this book is that it's just not funny. It takes the premise of a very funny book by Robin Cooper, called The Timewaster Letters
and changes the formula slightly.
In Cooper's book, spoof letters are sent to various customer services departments containing madcap ideas. Given that these departments try their best to be accommodating, they sometimes reply, even to the more outlandish ones. This can lead to a very funny correspondence.
However, in Nosy Neighbour Letters, all the letters are contrived, fictional. The humour vanishes when that element of genuine mickey-taking is lost - what you're left with is a series of letters that purport to be from an eccentric (who doesn't really exist), with replies from other people (who don't really exist). There isn't much to laugh at - I smiled once, but the whole thing is really just not that funny.
It's like watching a good episode of 'Beadle's About', and then comparing it to a set-up with actors replacing the gullible members of the public. It just doesn't feel real.
Don't waste your time on it - life's too short, and there's plenty of funnier alternatives to choose from.