It was written in 1397 by the scribe, Archdeacon Spiridon in Kiev, "at the command of Bishop Mikhail"; however, both scribe and patron had recently arrived from Moscow, and the decorations were probably added there later, in a refined and lively style, closely following a Byzantine 11th century Psalter.
Sometimes the meaning of the illustration is explained in long notes in the same thin red draft (apparently original).
The weighty and elegant script and large size of the page adds to the impressiveness of the book.
[1] The Psalter passed through the hands of numerous Lithuanian nobles before being sold to the Russian Count Sergey Sheremetev in the mid-19th century.
Courtesy of the count, its first printed edition was prepared by Nikodim Kondakov and Fyodor Buslaev.