The Brass Dragon is a 1969 science-fiction novel by Marion Zimmer Bradley, published as an Ace Double, with the other half being Ipomoea, by John Rackham. It is set in contemporary time, in 1967 and 1968, and deals with modern earth people discovering the truth of alien presence on earth.
Around the time I was reading this book, I formulated a general rule about what a reader might want when reading a book. And that is that a reader should want to know either the "what" or the "why" of what is going on, and hopefully in the first few pages. If the "what" is provided, the "why" can wait a little longer. And this book opens with a plot device that tells us "what": someone wakes up with amnesia. This isn't the most original of plot devices, but it immediately provides a driver for the plot. Our protagonist/hero, named (as we will both find out) Barry Cowan, wakes up in a hospital room in Abilene, Texas. He remembers that he is from the San Francisco Bay area but doesn't remember his name or his family. His suspicions are raised when a man claims to be his father, but Barry senses he is not. Cowan also feels something in his pocket, the titular "brass dragon", a small brass figurine of a dragon that he somehow feels is important. Luckily, he is soon recovered by a man who is his father---although Cowan can not remember him. Back in Berkeley, Cowan is still amnesiac, and he is starting to feel menaces from strange phone calls. His family's house is ransacked. The mystery builds up, with Cowan (and the reader) unaware of just who is pursuing him, and why. It is only after he returns to Texas and the doctor who helps him is assassinated that he meets someone who can help him---and then, in a long flashback that takes up the remaining half of the book, he suddenly remembers what happened.
The second part of the book, except for a short conclusion, is that flashback. Cowan accidentally met some good, peaceful aliens who are on an observational mission to earth are under attack by criminal reptilian shape-changing aliens, which leads to an interplanetary flying saucer chase, a trek across Mars, a Martian winter spent inside a base on Mars, some more fights, a trek back to earth---basically our mystery story is interrupted by a space opera, followed by a too-brief confusion where they return to earth and solve everything.
One of the major problems with this book is a problem that occurs in other science-fiction and fantasy books: the conflict between story telling and world building. The first half of this book was a taut psychological suspense story, with it all being a plausible story that hangs on the edge of mystery. But once things are explained, it loses part of its charm. During the second half of the book, when we are caught up to date about the exact diplomatic structure of the galactic federation, and the exact biology and social structure of the villainous aliens, the story takes place in a world that makes sense, but the entire literary point of the story, the tension of an amnesiac youth who is surrounded by eerie events, is lost. That is one of the two reasons why this story, which I felt was close to being a classic when I started reading it (like Damon Knight's The Sun Saboteurs), turned disappointing by the end.
The other reason has to do with Marion Zimmer Bradley's behavior in the real world. According to both plausible allegations and substantiated verdicts, Bradley and her partner Walter Breen were involved in molesting and sexually assaulting children, including their own, as well as covering up these acts. The strength and scope of the allegations is pretty repulsive. In this book, there is the barest hint of anything involved with that: when Cowan is in the hospital and a stranger attempts to take him home (that stranger being, as we will later learn, a shape-changing lizard person) the doctor considers it, saying
"He doesn't look like a pervert trying to get his hands on a kid, and even if he were, you're big enough to handle him. What are you afraid of?"
And without that knowledge of Bradley's crimes, this would maybe just seem like a reminder of a quaint time when "not looking like a pervert" was ID enough to pick up an amnesiac youth from the hospital (and indeed, this was a time when you could have a good chat about medical advice with your doctor while sharing a cigarette in his office). But, knowing what I know, there are other things in this book that feel a little wrong to me.