This is a traveling spellbook. It weighs three pounds; five such books will fit snugly in a backpack. It has a total of fifty pages.
A wizard cannot prepare spells from another wizard's spellbook, but the spellbook can be used to aid in one's own research. If a user of Arcane (Wizardry) Magicks attempts to research and learn a spell that is included in this book, using this book as a resource, he gains a +20% bonus to the research effort. (This benefit is not doubled if additional wealth is devoted to the research process, as described in Chapter Ten of The Missed Player's Handbook.)
This spellbook grants no additional benefit when it is used as part of spell preparation.
The picture at the back of the book is an image of the famous wizard Rul Thaven, an archmage of the House of Sages who perished fighting against the Lady Bevelon Halovic at the end of the War of Shadows.
The image implies that this must be one of her books. Likely, it is not a greater volume, but anything of hers is of historical significance, and certainly of arcane power.