
Castle Diary: The Journal of Tobias Burgess, Page by Richard Platt, 1999.
Tobias is an eleven-year-old boy living in England in 1285. He is from a noble family, and his father is sending him to his uncle to become a page. As a page, Tobias will learn manners and skills that he will need as he eventually becomes a squire and then a knight. During the first year of his training that he spends with his uncle, he keeps a diary of everything that happens to him and everything he learns. Toby is a fictional boy, but his life and family are meant to illustrate what life was like for a young boy from his social level during the Middle Ages.

The castle were Toby’s uncle lives is much bigger than his parents’ manor house. Toby has to learn the roles of all the servants who live there: who is in charge of what and who reports to who. Not all servants are equal, and some command more respect than others. Some of them are even from noble families like his, including his aunt’s companion, Isbel. Toby himself is assigned to do chores for his aunt like running errands, delivering messages, serving food at meals, and holding up the hem of her cloak when she walks outside.
Toby shares a room with the other pages at the castle, all boys of noble families and destined to become knights, just like him. They have lessons in reading, writing, mathematics, Latin, and scripture from the castle’s chaplain, and he is a harsh disciplinarian. They practice their lessons on wax tables that can be smoothed out and used again. The boys also learn manners and start learning archery and about all the weapons and armor that knights use. When they have time to play, they try walking on stilts and play at being jousting knights by carrying each other on their backs and trying to knock each other off.

During the course of the year, Toby gets to witness a hunt, a joust, and a banquet with important guests. At one point, he gets sick and receives treatment from a physician. He also encounters a poacher on his uncle’s land. This man is eventually caught (although Toby decides not to turn him in) and put on trial, but in the end, he is not punished because the jurors were sympathetic. The book ends with a Christmas celebration, after which Toby goes home to visit his parents.

In the back of the book, there is a section with more information about Medieval society, castles, sieges, weapons, armor, and the changes that eventually brought an end to feudal system that Toby knew.
The book is part of a series of historical picture books. It is currently available online through Internet Archive.

The Battle for the Castle by Elizabeth Winthrop, 1994.
The Treasure of Kilvarra by Elizabeth Baldwin Hazelton, 1974.
Without the amulet to protect her, Christie continues her search for the treasure. An accidental injury takes her to the place where it is hidden, but it’s a dangerous place. Caught in a terrible storm, the children explore an ancient stone tower. There, Christie sees the ghost of a long-dead monk, gesturing to her, begging her to follow him to the treasure that she seeks. The monk died protecting it, and it’s a very unexpected but wonderful treasure indeed. But, getting out of the place is going to be even more dangerous than getting in.
The Castle in the Attic by Elizabeth Winthrop, 1985.