A Prayerbook of Divine Service is a pristine leather-bound tome. Embossed upon its unblemished cover is the symbol of a celestial deity. The pages within are empty, bereft of scripture or arcane markings. However, its inner front cover houses a mystic golden plaque, which, when touched, reveals the below inscription and a collection of names scribed in various hands on the opposite page.

I hereby willingly bind myself to this Prayerbook of [Deity's Name], pledging my service to them and forsaking my own magical ambitions. In exchange, I am owed the gift of divine magics bestowed upon me by [Deity's Name]. This contract shall endure until [Deity's Name] deems their aims fulfilled and releases me from this agreement.

Not every deity finds themselves blessed with an abundance of mortal followers. For some, recruiting a handful of adherents is sufficient to begin their celestial renown, while others find themselves with pressing tasks that demand expedient completion and lack time to nurture a devout following. In the gravest circumstances, certain deities require willing agents to undertake missions that their own faithful cannot openly perform. In such moments, it is not uncommon for a deity to contract in external help.

By scribing your name below the list of previous signatories, you can attune to this tome. Upon attunement, select pages within it begin to unveil their hidden secrets, each functioning as a spell scroll, decipherable only by you. While attuned to the Prayerbook of Divine Service the spells displayed within are considered to be "on your class’s spell list" and "of a level that you can normally cast".

At each dawn you can choose a number of spells equal to your proficiency bonus from the Prayerbook of Divine Service Spell List, below, you may choose the same spell multiple times. However: the cumulative spell levels you choose cannot exceed your proficiency bonus, and no individual spell may surpass half your proficiency bonus in level. Each chosen spell appears on one of the pages of the Prayerbook, and functions as a spell scroll until you cast it or until the following dawn, in either case the words on the page then fade away.

Prayerbook of Divine Service Spell List.

Cantrips (0 Level)
Guidance
Light
Mending
Resistance
Sacred Flame
Thaumaturgy

1st Level
Bless
Command
Cure Wounds
Detect Magic
Guiding Bolt
Healing Word
Inflict Wounds
Sanctuary
Shield of Faith

2nd Level
Aid
Augury
Hold Person
Lesser Restoration
Silence
Spiritual Weapon
Warding Bond

3rd Level
Beacon of Hope
Dispel Magic
Mass Healing Word
Remove Curse
Revivify
Spirit Guardians

The Small Print.
I recommend leaving to individual DM's discretion how much of the small print is revealed when players attempt to identify this magic item.
This book is bound by contractual obligation, and becoming attuned to it commits you to the following contractual terms.

A Prayerbook of Divine Service contains a fragment of the essence of it's master. It possesses a limited sentience and will communicate with the signatory, through the transmission of emotions, to keep them aligned to the deity's goals.

Until the contract is fulfilled the signatory finds themselves unwilling to part with the book. They cannot sever their attunement to it unless the deity itself consents, and they feel compelled to keep it within arm's reach at all times.

Moreover, as the signatory has agreed to forsake their own magical ambitions, the book suppresses their other magical talents. While attuned to the Prayerbook of Divine Service, the signatory is unable to cast spells by any other means.

Notes: Damage, Buff, Debuff, Utility, Combat, Cursed, Sentient