Rare

How easy is it going to be to complete this collection? I have already stated my general strategy, i.e. concentrate on the hardbacks and let the paperbacks take care of themselves. I don’t think that there is really such a thing as a “rare” paperback Three Investigators book, although certainly some will be more difficult to find than others. From many years experience in buying Three Investigators books, here is my view on the relative difficulty you will find in obtaining the various editions:
Large Hardbacks
These can be split roughly into three groups. Books 1-16 and 18 will be the easiest to find in this edition. Most of these had more than one print run and they should be relatively easy to find. Books 17, 19 -23 are in the second group. Of these, only Phantom Lake and Monster Mountain had more than one printing. My experience is that these show up occasionally, but not as often as the earlier titles. Books numbered 24 to 28 fall into the most difficult to find category. If you manage to find one of these with its dustjacket that is not an ex-library book, you should be kicking your height. Of these titles, I have only seen one Death Trap Mine (and that was in appalling condition), two Dancing Devils (both in poor condition), two Headless Horses (one I bought myself new, the other a poor ex-library copy), One Magic Circle (again a poor ex-lib copy) and one Deadly Double, again a poor ex-lib version.
Small Hardbacks
Books numbered #1-18 should be easy enough to come across, as several of the earlier titles had multiple reprints. Books numbered 19-24 fall into the rare category, as these only had one printing and are generally difficult to find. I would put them on par with some of the later large hardbacks to find, especially Monster Mountain, Haunted Mirror, Invisible Dog and Death Trap Mine. I think I have only ever seen one or two at most of these editions.
Paperback 1
These should all be very easy to find, with the possible exception of the first Vanishing Treasure imprint, which featured the cover with the boy brandishing a knife.
Paperback 2
Again, these are in plentiful supply, even the last one in this set, Shark Reef shows up frequently.
Paperback 3
This is where you will start finding difficulty in obtaining some titles. You may find, as I did, that many of these will be available as ex library copies. The last few titles in this format are not so easy to come by, with Smashing Glass, in my experience, the hardest of the lot to find.
Paperback 4
You may find these among the hardest to find. My old collection included several of these as ex-library books. You will probably find some of the later titles quite difficult to find, particularly Missing Mermaid, Two Toed Pigeon, Creep Show Crooks and Wrecker’s Rock, although none of them are anything like as common as paperback editions 1 and 2.
Paperback 5
Being the last imprint before the series went officially out of print, these books were heavily remaindered in book outlets such as Bargain Books and BookWorld. For some reason, I found many of these titles difficult to track down, but when I did find them, they were generally in very good condition. In fact, back when I was putting my last collection together, you could still find these in bookshops such as Waterstones, and I remember getting a brand new copy of Haunted Mirror in a bookshop in London to complete my set.
Three Investigators Omnibuses
You should not find much difficulty in adding any of these to your collection, beware though, as they are frequently in poor and well read condition. The Diamond editions were heavily remaindered through Bargain Books etc.
Crimebusters
The early titles are fairly plentiful, the later ones slightly less so, however you should not experience much trouble in putting together a complete set quite quickly. The Crimebusters omnibuses are ten a penny. Don’t buy unless it is in mint condition, as there will be a better copy along soon enough. I suppose the true purist will want Mulberry and Diamond imprints in his collection.