Mervyn Peake's output was varied; he was a poet, a novelist, a playwright, and an illustrator. All of these skills come into play in his fantasy trilogy "Gormenghast", published in 1946 ("Titus Groan"), 1950 ("Gormenghast") and 1959 ("Titus Alone").
The Gormenghast trilogy (***+) is unique -- a triumph of skill over what looks at first sight to be an impossibly unpromising premise. We start with an enormous castle, Gormenghast, which seems to have been borrowed from a Gothic novel on steroids. We people it with refugees from a Dickens novel. They have names like Prunesquallor and Swelter and Flay and Sourdust -- not to forget Lord Sepulchrave, the seventy-sixth Earl of Groan -- and their characters often match. Finally -- this is important -- we don't play it for laughs. We take these people at their self-estimation and enter a world where Gormenghast is as much of the universe as matters. It takes remarkable control to pull that off, and Peake possessed it. The reader soon ceases to notice how mad a world s/he's entered.
"Titus Groan" (****-) is the first book of the trilogy. Titus himself is the son and heir of Lord Sepulchrave and, in principle, the trilogy is his story. It is significant that the trilogy takes its name from the castle, rather than from the boy -- and that the book that is named for him ends when he is two years old. Gormenghast overshadows Titus. The castle is by far the most important 'character'. It's impossibly large, and impossibly old -- a self-contained universe. (We learn at the start of this book that outside of the castle grounds are a cluster of primitive dwellings. It isn't until book three that we find out that there's a larger outside world.)
Gormenghast is also impossibly stagnant. There are rituals, centuries or millennia old, governing every hour of the day. There are armies of servants doing exactly what their ancestors did. People who live in the castle become as grey as its walls. (It's hard to imagine Gormenghast as a place for song, or for love.) Oh, there's plenty of room for eccentricity, but someone eccentric enough to actually combat the castle's inertia would probably be steam-rollered without anyone noticing. There are important positions within the castle, but there are always replacements for the self-important people who hold them. (We know the replacements were once children, with fathers and mothers, but it's hard to avoid the feeling that the castle just generated them, already old, when they were needed.)
The worm gnawing away at Gormenghast is a youth named Steerpike, who thinks he wants power, but really wants destruction. We first encounter him in the Great Kitchen, the newest apprentice to the vile chef. It shouldn't be imagined, despite his rhetoric, that this beginning instills any moral indignation. He is opportunistic and self-centered, and once he has bettered his circumstances, he sets out to do so again. He exploits those he can, and destroys those he cannot. At the end of "Titus Groan", Lord Sepulchrave is dead and his heir is two years old. Steerpike has wormed himself closer to the center of power, but is still unnoticed by most. The routine of the castle continues as always, and if some of its supports have been eroded or destroyed, it's possible not to notice.
"Gormenghast" (***+), the second book of the trilogy, begins five years later, and covers the period of Titus's youth. Steerpike rises in position and power, continuing to leave a trail of death and destruction behind him, coming nearer to taking control of the Gormenghast juggernaut.
In one respect, he fails. His personal ambition is not realized. His destructive impulse, however, succeeds in an unanticipated way: By the end of the second book, his actions have left Titus with the awareness that there is a world beyond Gormenghast, and with the desire to see it: Titus leaves.
"Titus Alone" (**), which follows Titus into the outside world, is disappointing. Different people will give you different explanations, the most commonly heard being that Peake was dying when he wrote it, and left it unpolished. (For what it's worth, Peake died in 1968. The 1970 edition of "Titus Alone" contains extensive posthumous corrections to the 1959 edition.) I'd offer a much simpler explanation: "Titus Alone", as the title implies, is just about Titus. The book lacks Gormenghast -- by far the most interesting 'character' in the trilogy -- and it lacks all the other characters who inhabited it. Except insofar as Gormenghast has shaped Titus, this book is almost unconnected to the other two.
No, that's not quite true. It's thematically connected -- the outside world is as strange and as rigid in its Dickensian way as Gormenghast is in its Gothic self-involvement. But it's a far less interesting world. What it comes to is that reading "Titus Alone" is a let-down.
Reading "Titus Groan", however, is worth the effort. At least, I thought so; it's not going to be to all tastes: The book is demanding, dark, sometimes ugly. It's also brilliantly written and, once you enter its world, captivating. I expect that most readers who finish "Titus Groan" will also finish the rest of the trilogy.