[Big up-front disclaimer - this is amateurish, random & composed of wild speculation. Take this seriously at your own risk. That said, I'll try to clarify my reasoning where I can, so you can form your own conclusions.]
Before City of Ruin, before Nights of Villjamur, way back in the misty past of 2008, a young author named Mark Charan Newton made his debut with The Reef.
The Reef features a group of academic adventurers exploring an island filled with mysteries. Combining politics and squid, it is a rough, entertaining and surprisingly thoughtful early effort from the author.
However, as much as I like it, I'm not looking at The Reef for its literary merit. Despite its relative recency, I think The Reef has earned a place as a collectible title for several reasons, all listed below.
1) Scarcity. As of right now (well, as of writing this post), there are three copies for sale across all book search engines, eBay and Amazon. Of those three, the selling prices range from $14.99 to $150. This isn't completely unexpected - only 300 copies of The Reef were printed. According to the publisher, Pendragon Press, there are no further printings planned.*
2) Bet on the author. The Legends of the Red Dawn series has been contracted for more books, as well as US publication. Not to keep bandying the word "young" about constantly, but this is a commercially-savvy author at the beginning of a, potentially, very lengthy and storied career.
3) Completists. This is where The Reef's quality does make a difference - it isn't a fumbling adolescent effort, it is, properly, a first book. Also, unlike, say, a short story contribution to a larger collection (which, except for H.P. Lovecraft, won't ever be worth an exceptional amount), Mark Charan Newton's first effort was a proper book of a book. More appealing, more attractive on a shelf & more collectible value.
Finally, The Reef is written in the same genre as the author's popular books, so as he continues to gain success as a fantasy author, The Reef will continue to be relevant to his fans. (Unlike, for example, George R.R. Martin's earlier works.) It is a shame that The Reef came out as a paperback, but at least it is trade-sized and well-made.
The best case scenario would be a comparison with Joe Hill - a popular genre author whose early publications were also small print runs for small presses (including the British PS Publishing). These now command fairly spectacular prices.
The worst case scenario is still fairly rosy. At 300 copies, from a respectable publisher and a good book in its own right, it would take a perplexing twist of fate to make The Reef fall below RRP. With the author poised to make even more noise on the market, that seems extremely unlikely.
Interestingly, despite its scarcity on the rare books market, a few copies of The Reef are still on the shelf at various Waterstone's stores. £100 online... or £10 in the shop. Something has got to give.
Conclusion: Especially given the existing (if limited) opportunity to nab copies of this book at RRP, this seems a sure thing.
*Interesting fun fact: There's a 28-copy "lettered" version of The Reef, but this isn't actually a separate printing. A dealer purchased 28 copies from the publisher and had the author sign & letter them in his own handwriting.