claim: Therasia is a European island.
evidence: Ace Books have published hundreds of mystery titles , starting in 1952 .. Ace Books. Ace Books. mystery. mystery fiction. Most of these were Ace Doubles -LRB- dos-a-dos format -RRB- , but they also published a few single volumes .. Ace Doubles. List of Ace Mystery Double Titles. dos-a-dos. dos-a-dos binding. Between 1952 and 1968 , the books had a letter-series identifier ; after that date they were given five digit numeric serial numbers .. There were a total of 17 letter-series mystery titles .. mystery. mystery fiction. The list given here gives a date of publication ; in all cases this refers to the date of publication by Ace , and not the date of original publication of the novels .. For more information about the history of these titles , see Ace Books , which includes a discussion of the serial numbering conventions used and an explanation of the letter-code system .. Ace Books. Ace Books