"Suppose he's one of those very clever coots you read about in detective stories-"
"Especially yours," muttered the old man.
"-especially mine," nodded his son, "And Rex's, and John's, and Miss Christie's, and other practitioners of the delightfully improbable. And suppose he's playing a game with you-- us."
"The Player On The Other Side" (Ellery Queen)
Just a few more Queens left before I've gone through them all!

The Player On The Other Side is a late Ellery Queen novel, ghost-written by Theodore Surgeon and extensively revised by both of the Queen cousins (Dannay and Lee). For what it is worth, it does feel like a regular Queen most of the time and builds on the themes that had been going on in the 'proper' Canon in an interesting, if not always satisfying manner.
The novel starts with Ellery lamenting that time and technology has caught up on him and that he, as a detective, is not needed anymore. The York case brings Ellery back in the game, and it's a game he is very familiar with. Whereas a lot of Queen novels featured twist endings where it is revealed that everything, including a scapegoat murderer, had been manipulated by the real murderer, we are told right away in The Player on the Other Side that Walt is being controlled by "Y", the titular Player on the Other Side. It does bring a slightly different dynamic to reading this Queen for me, because I usually read later Queens distrusting everyone and everything like I'm suffering from paranoia, as I always anticipate a twist ending.
I do have to say though, The Player On The Other Side, feels a bit predictable, even in its twists and turns. A lot of elements have been used in earlier Queens already: a private square in New York has been used already in the series (The Greek Coffin Mystery), just like the slighty disfunctional family (There Was An OldWoman), a family called York (The Tragedy of Y), mysterious letters sent to the victims ("The Mad Tea Party", The Finishing Stroke) and like I mentioned, the Manipulator (would be kinda spoilerish to mention specific titles, I guess). I guess that this story is exactly what Ellery wished for, 'a case like always', but it feel too familiar at times.
Loyal Queen readers won't have any trouble figuring out most of the mystery behind the letters sent to the victims, I think, as it's a theme that popped up quite often in later Queen novels (in fact, I thought it kinda strange that it took Ellery that long to figure it out). Overall, I don't dislike the solution, but it is definitely not perfect: the hinting is a bit weak and while I am usually the last to complain about motives, especially a Queen novel, this time the motive behind the murders is quite important to the solution, and it's... well, not convincing here. Thematically, I can see where the Queen cousins and Surgeon were heading for and I do like the idea, but I feel the execution could have been a bit more neater, a bit more clearer.
Overall, The Player On The Other Side is a decent Queen novel though, ghost-written or not. I do think it's a novel better read in the context of other, later Queen novels, or else the solution might seem a bit too farfetched, but on the other hand, a lot of elements do seem a bit too familiar if you've read more Queens. All well, three more Queens to go!