Books of the Anvil - A Downtime Magic Item for 5e

The Books of the Anvil are a legendary collection of collected over the years by an unknown master
Dwarfish wizard. With typical Dwarfish ingenuity and discipline, he applied himself to cataloging magic with the same intensity of focus that a master smith would bring to a life-long masterwork.

Identifying the Books
Even to the untrained eye, this collection of 15 books (50 lbs total) appear to be of exceptional quality. Despite their antiquity, they are in exquisite condition. Each page is richly illuminated, with orderly black-on-white lettering interspersed with geometric designs and diagrams. To Detect Magic they give off an aura of mild divination and abjuration magic. Any wizard can immediately recognize that the books are all spellbooks, as can anyone making a DC 5 Arcana check. On a DC 20 Arcana check, you recognize the books as being those of a Dwarfish wizard. Anyone who knows the Dwarfish language and is of Chaotic alignment must make a DC 15 Wisdom save on first reading through the books or be blinded for 1d10 hours. Subsequent readings have no effect on a character who has been blinded, though overuse (described below) can still trigger blindness.

Using the Books
The Books of the Anvil use a highly complex magical encoding scheme to cram a seemingly impossible number of spells into 15 volumes. Unfortunately (for everyone but Dwarfs) this means that a great deal of math is needed to puzzle out the spell formulas, and a table of contents is neither included nor possible.

A wizard can chose to study the books for up to 8 hour per day. Time spent resting or adventuring does not permit proper study- the books can only be studied on 'days off', though other non-strenuous activities (buying supplies, resting and healing) can be undertaken. A wizard who attempts to study more than 8 hours in a single day becomes blind for 1d10 hours. At the end of 7 (cumulative) days of study, make a DC 15 Arcana check. On a success, the wizard has identified one spell that is stored in the book and can attempt to learn it and copy it into his spellbook as normal, paying the associated costs in time and gold. Determine the spell randomly. If the wizard chooses not to learn the spell, there is no guarantee that he will be able to figure out the encoding for that spell again- each time the wizard attempts to identify a new spell, the encoding for the previous spell is forgotten and a new spell is generated at random.