Spell Mechanics

Your party will know some spells, and not know others. ‘knowing’ does
 not mean you are proficient in them in any way (yet). The party will
know some basic spells from the start, because everyone has heard of
them or seen them in practice. Again, this does not mean everyone can
cast them.  If you find a spell book
of a previously unknown spell, the spell becomes known to the party.
Known means the picture and description will appear if you select it in
its spell group in the ABILITIES -> SPELLS section

If you know a spell, and a player has talent points to spare, in
theory he can spend one to improve his spell proficiency in that spell,
assuming:
a) his class cap for that spell isn’t already exceed by him. A cleric
can learn the spell magic missile, but he will never be really good at
it. Just not his cup of tea.
b) his spell proficiency has not already reached or exceeded his magic
lore skill. to STUDY a spell via talent points means to improve what you
 are doing, and that requires knowledge about how the fabric of magic
and this particular spell works. Most spell casters can be trained in
this, but some better than others. Studying magic extensively is the
specialty of wizards and geomancer and to some extent priests.

If your proficiency is at least 1, you can cast a spell. All spells
are displaying their ‘level’ in roman numbers. Simply to visually get an
 indication how powerful you are casting the spell. Roman I means
proficiency of 1-9, II means 10-19, VI means 50-59 and so on.

When you cast spells, you will eventually get better at them. How
fast / how many practices it takes is different for each spell and I
won’t reveal the exact figures. I don’t want spells like magic missile
that work on auto to go up in proficiency every other fight. That would
make it too powerful too quickly.

The class max limit does NOT apply for learning by doing, you can
always become a FREAK in your class by doing things others in your class
 don’t normally do. I am yet looking forward to someone dedicating some
time building a druid with a “divine widow maker of shock” (a ranged
weapon) with a ranged weapon skill of 99, casting HASTE at spell level
10 and basically knocking an army of golems out of the park in a matter
of seconds. Possible, yet quite a task to complete …

NPCs can also sometimes give you knowledge (and sometimes starting
proficiency of 1) in a spell. I think holy smite and holy plasma gets
awarded by an NPC from memory.

On class change, all classes gain a few proficiency points in either
new, or existing skills or spells that the new class is specifically
good with.

SPELL BOOKS help magic users boost their spell proficiency through
‘study'(use of talent points). They can study regardless, but with books
 it yields bigger proficiency increases. You are capped though in this
method by your magic lore skill.
Books can be seen for each spell individually in the spell’s details when looking at ABILITIES -> SPELLS.

If you find a spellbook, it has a ‘rank’ which is represented by its
name.  “Basics of” is a low rank.  “Tome of” is a higher one.  When you
find one you already have, it is worthless.  However the game checks if
there is a lower level one you don’t already have and changes it to that
 if the case.  Having a high rank and low rank book is better than just
having the high rank one.

Common places to find spellbooks are: when defeating a spellcaster
like an orc mage (low chance) or a beholder (high chance) or a conjurer ;
 when looting the top level of the lich tower (several are found there);
 when finding rare hideouts of spellcasters (there is one hidden away
deep in the watery caves when you follow the river up into the mountain,
 just west of the starting shelter. If a spell is generally known, but
your proficiency is zero, then you can learn it as well by spending
talent points. For example if you have a druid and a mage in your party,
 they can effectively learn each other’s spells this way.