The only other collection of hoax letters that I'd read prior to reading this was Cooper's Timewaster Letters. I must say that this collection compares unfavourably. Where to start? Hebblewhite's letters consist of large paragraphs that aren't easy on the eye. It's irritating to read large chunks of text in small print. I keep skipping lines. Then there's no "end of correspondence" or "no reply" stamps where they apply. They just made things simpler and broke up the monotony.
Three: (and this is quite an elementary flaw) not many of his second letters got a reply! In fact, if I'm not mistaken, I think his first successful second letter came on page 60! In that sense these missives are the letter-writing equivalent of happy slapping or pressing a door-bell and running away. He doesn't succeed often in reeling in his victims and stringing them along like Cooper does. In some ways this is understandable or, if not, at least excusable.
However, what's less understandable is (four) failing to reply to a victim's letter. On a number of occasions his target replied to one of his letters and didn't appear to have sussed that this was a hoax. Yet Hebblewhite seems to have chickened out. I can't think of any other reason he'd let pass such opportunities to cause further mischief. Examples being Handlebar Club (p. 103), Welsh Black Breeders (p. 129) and Inspectorate of Mines (p. 217) to name just three.
Lastly, there was a definite lack of a theme to these letters. No unifying sense. I didn't detect a personality or character behind them. So I don't think we'll see The Wind-up Diaries a la Timewaster. Since all that would entail would be a person writing random hoax letters. To return to the Timewaster comparison, in some ways there are similarities. The humour is gentle, not malicious. There is the odd poem. Though there aren't many drawings or diagrams.
To conclude. This is funny in places and the perfect book to have on the coffee table to dip into occasionally. Don't attempt to read it cover to cover as it quickly becomes repetitive. Like I said, not as good as Timewaster Letters by Robin Cooper.
P.S. There is a missing letter! Between pp. 195-196 there should be another Hebblewhite letter. It is referred to in those that follow.