There is much overlap between this 1974 book by Peake's widow and a collaborator, and Peter Winnington's "Mervyn Peake: The Man and His Art" (https://www.goodreads.com/review/show...) from 2007. This one is limited to black and white, but in addition to his art, it includes significant excerpts of his writings: poems, novels (including parallel passages of an early and late draft of "Titus Groan"), and apparently, the whole of "The Craft of the Lead Pencil". The layout isn't great, so you have to keep your wits about you, but it's worth it; the former is also true of this review!
The tragic and beautiful cover picture is of Jo, a crossing sweeper, from Bleak House, which was Peake's favourite Dickens. See "Sketches from Bleak House" (https://www.goodreads.com/review/show...).
This book opens with a three-page biography by his widow, after which it is a sweeping, chronological overview of Peake's works, but linking his works to events in his life, his health etc. I've summarised much of this in my review of Maeve's memoirs, but the key points are that he was born and raised in China until the age of 11, went to boarding school, then art school, did national service but was invalided out after a nervous breakdown, became a war artist and was traumatised by what he saw at Belsen, died prematurely of a combination of Parkinson's, depression and the treatment thereof (but it took a decade).
One key point is that Peake was initially very much an artist (he went to art school and later taught, as well as taking commissions); writing was a private hobby, and most of his writings were illustrated anyway.
Some of his thoughts about art are covered: the fact that the text he wrote is called "The Craft of the Lead Pencil" is significant, as is demonstrated by the content included here. He exhorts students to learn to see and to be expressive - skills that are also evident in his writing.
He also says, "Line... is language" and "Rhythm - a quality inherent in all forms of art". It is possible that Peake was a synaesthete: in her memoirs ("A World Away" -https://www.goodreads.com/review/show...), Maeve mentions that he tended to think of each number as either male of female.
In addition to "The Craft", Peake explained his theories of drawing in a lengthy introduction to a collection of his drawings, but I don't think he ever wrote about writing in the same way.
I've reviewed Peake's writings at length in individual reviews (see my Gormenghast-Peake shelf:https://www.goodreads.com/review/list...). However, I will mention this painful poem, written during a hospital stay:
"Heads float about me, come and go, absorb me;
Terrify me that they deny the nightmare
That they should be, defy me;
And all the secrecy; the horror
Of truth, of this intrinsic truth
Drifting, ah God, along the corridors
Of the world; hearing the metal
Clang; and the rolling wheels,
Heads float about me haunted
By solitary sorrows."
In 1941, poet Walter de la Mare wrote an amusing fan letter about the illustrations to a book of Nursery Rhymes, concluding:
"How many nurseries you may have appalled is another matter. How many scandalised parents may have written to you, possibly enclosing doctors' and neurologists' bills, you will probably not disclose. Anyhow, most other illustrated books for children look silly by comparison."
CS Lewis described "Titus Groan" and "Gormenghast" thus:
"It has the hallmark of a true myth: i.e. you have seen nothing like it before you read the book, but after that you see things like it everywhere."
I'm not sure I agree with that, but it's something to ponder.
In addition, Winnington mentions that Elizabeth Bowen was a fan, and Joanne Harris is one too.
Peake concurrently portrayed contrasting views, such as portraying Swelter (in Titus Groan) as a ship in full sail and a mass of shifting lights and colours.
There is an anecdote about an unpleasant encounter with a camel in China when he was a boy, which is used to explain the number of nasty camels that crop up in his works, and that I hadn't really noticed.
There is a good bibliography of works by and about Peake.