This has the potential to be a fantastic resource...
Most fantasy RPGs have some kind of religion knocking around: the 'Cleric' or equivalent is a standard trade amidst the adventuring classes. Yet each system's treatment of their clerics is based on things like spellcasting, healing and fighting with deities - who ought to be central to any cleric's life - being somewhat left in the background, a notation on the character sheet. So here is an attempt to address this, with ideas about the ways in which a cleric goes about his business, god-centred ways, even if what he actually wants to do is cast a spell, heal someone or defeat an enemy!
Consider real-world religion for a moment. Even if you don't happen to practise one yourself, you know that religions tend to be big on ritual and ceremonial when they approach their deity. They can be quite spectacular, like a Roman Catholic High Mass, or more simple yet full of formal words and actions - perhaps you have seen a Muslim saying his prayers. Do not the deities of your fantasy world command the same respect from their devotees?
To help you create the cultural aspects of the religions practised in your campaign world, the author has drawn on both game mechanics and the sorts of rituals and ceremonies common within religion to suggest ways in which to bring out the god-centred approach of an RPG cleric, using ceremonial to request his powers and then using them in furtherance of his in-game ends. It looks at preparing and performing ceremonies, at ritual trappings, at incorporating music and special clothing and prayers to set apart the ritual from day-to-day life.
This is a toolbox of ideas, a collection of things to think about. Some examples are given, but this product's real strength is in helping you create ceremonies and rituals based around whatever religions you have in your game world, giving your clerics - PC and NPC alike - a meaningful focus as priests rather than magicians who just happen to get their powers from a deity rather than book-learning. The one drawback - and the reason my rating is 4 stars not 5 - is that the whole thing is written in a crabbed script that is very hard to read! Nice look and feel of some ancient manuscript, perhaps, but even though I can read secretary hand (the common scrawl of the mediaeval scribe) and have a big monitor, I am having to peer hard to make out what is being said... but it is worth making the effort, if you want to bring a proper air of mystery and religious power to your clerics.