The English word "book" has many potential Latin translations, such as liber, monumentum, carta, codex, and volumen.
If, in this context, the book refers to a textbook or collection of stories, what would be the most accurate Latin word to use?
Liber is that Latin word for book, and my first inclination is to go there. However, further context is needed to make an actual decision. Other options include libellum and codex.
Monumentum is most wrong. A book can be a monument, but not all monuments are books, and so likewise not all monumenta are libri. If you're refering to the Horace quote monumenta rerum gestarum, yes they're written down, but they're memorials of deeds. It's a metaphor.
Charta and codex refer to the thing a book is written upon. It refers to the material. So a book of Cicero, a liber Ciceronis can be written on chartae or placed in a codex. However, collections of works in book-form are often called a codex, so depending on what exactly you're describing, this might be the best word after all. As a solid example, a collection of laws published by Theodosius is called the Codex Theodosianus. Bibles were often written on codices, so that you have e.g. Codex Sinaiticus, an ancient codex upon which the New Testament was written.
Volumen, too, can mean that, though of the options, it's the closest to liber. However, it might help to remember the etymological role of the word. It comes from volvere "to roll", and referred originally to rolled up papyri. In that sense, since a work was usually on multiple papyri, it refers to a part of a full work, similar to the word "volume" today.
To be fair, liber can mean all these things, too. A work of Cicero's, let's say the De Natura Deorum, would have been described as being in libris tribus "in three books". But as L&S note, it's most commonly used as a single work, either in singular or in plural.
Finally, libellum refers to a little book, and is what Catullus used to describe his short collection of poems.