Sorry for the delay, the internet broke soon after you asked. I suggest saying Romance Of The three kingdoms three times in front of a mirror, see if Dong Zhuo appears

We do have a Book List just in case anything catches your eye.

I don't know if your coming at this from a game, movie or something else or if "I have read the novel, want to know the history." So I'll try to cover all bases with this answer.

The Romance of the Three Kingdoms is unhelpful as a history book due to the scale of its fiction and the way it reshapes the era. It is the basis for modern portrayals across entertainment, influences heavily the way people see the era and figures. So it is something that should be read at some point if you haven't, to help understand where others come from, and is an entertaining read. Go for unabridged (and check carefully that it is unabridged), Moss Roberts translation is the classic and I would advise avoiding the C.H. Brewitt-Taylor versions as they used the Wade–Giles system so Cao Cao becomes Tsao Tsao, Zhuge Liang becomes Chuko Liang. Those may be simple but those are two of the most characters, there are so many characters in the novel and not all are so easy to recognize in the Wade-Giles system.

I can't think of a good book on the history of the creation of the Romance or the impact it has had. Perhaps oddly now I think about it. History works will sometimes touch upon the romance and the shaping of reputations in history before it gets to the romance, some history works are specifically on the shaping of certain figures in popular mindset before the novel. But nothing specifically on the novel.

I know a few things about the era the novel covers, the collapse of the Later Han, the three kingdoms up to the unification. If you are coming at this after reading the novel, I would advise you to treat the novel and history version of the three kingdoms as two very separate worlds. The novel follows some of the structures from history but the world set out by Chen Shou in the SGZ (records of the three kingdoms) and one set the novel is very different. People have very different personalities and abilities, warfare is carried out very differently, a lot is cut out by the novel for narrative/length sake that would shape decisions taken by the historical figures (and dynamics between the factions), the novel has themes that it fits events into. Merging the two leads to a lot of errors in understanding the history and the people of it.

Rafe De Crespigny, one of the leading western experts on the fall of the Han and the build-up to the civil war has put a lot of his work up online for free. He has an easy and sometimes humorous writing style that should help ease you in and do it for free before deciding if you wish to pursue history with payable books.

He has an overview: The Three Kingdoms and Western Jin: A History of China in the Third Century AD (Part 1, covering till Jin unification) as a quick starter. There is a translation of Sima Guang's ZZTJ which acts as a year by year overview of the era (with notes from De Crespigny) for the years from Emperor Ling's death to Cao Cao's death under To Establish Peace. The reigns of Emperor Huan and Emperor Ling can also be found there.

He also has many articles there like Xun Yu's death or about women (and how they were treated) in the later Han if you want to look around. In terms of a good (and free) full book it also includes his seminal work on the kingdom of Wu, Generals of the South. They are rather sidelined in the novel and culture but the book shows the great talents and achievements of the kingdom of Wu.

If you have the spare cash, Empress and Consorts by Robert Cutter and William Cromwell is a good starter text for someone entering the era. It is a bit old but should be fairly cheap, it acts as a good introduction to the records of the three kingdoms by Chen Shou and Pei Songzhi, using Lady Zhen's death as a useful beginner guide on how to read the historical texts. The biographies of the Empresses will also give a sense of what Chen Shou's records look like (and how bad Shu-Han's records are) and if that is a route you want to go down.