Let's look at how spell books are handled in Holmes Basic. First, note they are never referred to as "spell books" per se - instead they are called "magic books":
"The magic-user acquires books containing the spells, the study of which allows him to memorize a spell for use ... More important, as the spell is recited it fades from the spell-caster's mind and he can not use it again! He must go back to his study and re-learn the spell. This takes at least 1 day. Magic-users can not bring their magic books into the dungeon with them. Always assume that more than 1 day has passed between expeditions, so that a magic-user who leaves the dungeon and goes home may start a new game with all his spells ready, but the appropriate time lag must be carefully noted" (pg 13).
From this we also learn:
-M-Us can't bring their spell books into the dungeon
-It takes an entire day to re-learn spells (i.e., not just after a night's sleep)
-The use of the plural "books" is because M-Us have one book for each level of spells. The lists of spells are called "Book of First Level Spells", "Book of Second Level Spells" etc. This is from OD&D, Vol 1, which states: "Characters who employ spells are assumed to acquire books containing the spells they can use, one book for each level" (pg 34)
The 4th level M-U in the Sample Dungeon has "two giant volumes of his magic spells" (pg 45) - presumably one for 1st and one for 2nd level spells. The size explains why they can't be carried in the dungeon. I'm not sure where Holmes picked up this rule. In the OD&D FAQ in Strategic Review #2 (Summer 1975), Gygax states that a M-U "can use a given spell but once during any given day, even if he is carrying his books with him", which indicates he let M-Us bring their books with them. OD&D also provides costs for replacing spell books.
The spell books are also mentioned under the rules for spell research and for learning spells. Successfully researched spells are written in the book. A new M-U must successfully copy spells from the "Book of First Level Spells" into the personal spell book. All of the standard 1st level spells are available to be learned by new M-Us, but chance of learning and number learned is dependent on INT.
In Dragon #52, Holmes reviewed the new Moldvay Basic Set and wrote: "Magic and spells: the new rules specify that if an adventure lasts longer than a day, the Magic-User can get his or her spells back through a period of rest and concentration. I'm glad to see this securely placed in the rules. All of us who act as Dungeon Masters have had to allow this on longer adventures. Actually the "spell book" is often a needless complication and can be dispensed with. Of course, a particular DM can make spell books a vital part of the game - suppose evil Magic-Users hired a high level Thief to steal the player characters' books?"
To solve this problem, a Holmes DM could simply allow for re-memorization from scrolls. These could be bundled to create a dungeon-ready magic book (dungeon book). In B2, a blank vellum book costs 20 gp (at the Bank in the Keep). Adding a known spell to the dungeon book requires the same cost/time as constructing a scroll. In a pinch a spell can be cast directly from the book as a scroll, but it then disappears and the magic-user must once again return home to his magic books to learn the spell. Furthermore, due to the cost and time for enchantment, the scroll or dungeon book acts an a mnemonic enhancer and allows memorization after a night's sleep rather than requiring a full day of study.