Hello everyone !
First post here, as I just fell in love again with D&D thanks to those absolutely awesome new 5th Edition rules (I've been playing on and off since the Basic red box in 1983 or something, but those new rules made me want to play regularely again, so we've just started the "Rise of Tiamat" campaign with some friends).
Anyway, here's something I'm a bit confused about, concerning Spellcasting : "You can change your list of prepared spells when you finish a long rest."
Does that mean that every spellcaster (Cleric, Wizard, Sorcerer, ...) has access to absolutely any spell from the Player's Handbook (from his Class), and can just pick the ones he wants to have "prepared" for the day ?
The Wizard class has a mention of a spellbook, which could indicate that he would have to choose a few spells per level that would be featured on his spellbook, then choose from those spells the ones he wants to prepare for the day, but it doesn't seem very clear to me (but I probably missed something) ?
The other Classes don't even have a spellbook, which seem to mean that they have access to absolutely every spell there is, and just need to choose some of them according to their level ?
That seems a bit weird to me, having access to every spell without even learning them somehow, that doesn't make any sense "in-character" speaking, but again I probably missed something somewhere, any clarifications would be greatly appreciated 
Thanks !!
Each class has a description in their write-up of how they learn their spells and how many they can prepare every day. It differs from class to class. Clerics and druids can choose any spell from their entire list when preparing spells. So can Paladins. Wizards do not know all the spells on their class list. They are limited to knowing a certain number of spells at 1st level, gain two more each time they level up and can also find more while adventuring. Sorcerors, Bards and Rangers are limited to knowing only a certain number of spells per character level, although sorcerors and bards can replace lower level spells when they level up. Warlocks also know only a limited number of spells by class level, although their spell slots are handled differently.
Wizards do not know every spell listed.
Wizards start out knowing *three* cantrips, which they can cast at will, and learn new ones every so often according to the chart in their class description.
They also start out knowing *six* 1st level spells. Wizards gain two new spells in their spellbook every time they gain a character level (plus any others they may find while adventuring), and must prepare their spells every day from the list of those in their spellbook.
Wizards can *prepare* a number of spells equal to their INT modifier plust their wizard level, and can then cast them in any combination according to how many spell slots they have.
Sorcerors start off with *four* cantrips, and learn more according to their class chart. They start play with *two* 1st level spells and only ever learn new spells according to the Spells Known column of their chart, although they can replace lower level spells with higher ones when they level up.
Bards start off knowing *two* cantrips, and learn more at certain levels according to their chart. They begin play with *four* 1st level spells. They only ever learn new spells according to the Spells Known column of their chart, although they can choose to replace a lower level spell with a higher one when they level up.
At 10th, 14th and 18th level, they also learn two spells from *any* class list that don't count toward their regular limit of spells known.
Clerics start off with *three* cantrips they can cast at will and learn more by level according to the chart in their class description.
- Unlike wizards - Clerics can choose to prepare *any* spell on the cleric spell list as long as they're of sufficient level to cast it.
They can *prepare* a number of spells per day equal to their WIS modifier plus their cleric level. The number of spell slots they can use per day is found on the chart in their class description.
Each cleric also chooses a Domain, which gives them additional spells that don't count towards their limit of regular spells prepared or per day.
Druids learn *two* cantrips to start with and then advance according to their chart. They don't get Domain spells but are otherwise identical to clerics in regard to spellcasting.
Paladins can *prepare* CHA modifier plus *one-half* character level spells per day, choosing from any spell on the cleric list. They gain no cantrips and their spell slots per day are listed in their chart.
Rangers don't gain spells until second level. Then you gain two spells known, from the Ranger spell list, and the number of spell slots listed on the chart for their level. Rangers, like Bards, only ever gain new spells known when they level up.
Warlocks start with two cantrips and gain more as they level up. They also start with *two* first level spells, gain new spells known only as they level up, and can replace lower level spells as they level up - however, all of their spell slots per day are of the same level (as listed on their chart)...
Now THAT is very clear, precise, and perfectly explained, thanks a lot for taking the time to write this ! 
Only Divine magic is available "at will" then, I guess we can say that the characters' Deities have enough power to know every existing Spell then grant them to their followers, while Arcanic magic has to be discovered and researched by each character ?
It actually makes a lot of sense, just like everything in those awesome new rules 
Thanks again, like I said I was sure I missed something somewhere, but as English is not my native language, sometimes it happens 
It may be helpful to divide the classes into three groups:
Bard, Ranger, Sorcerer, Fighter (Eldritch Knight), Warlock, and Rogue (Arcane Trickster)
You have a limited list of spells that you know. The only way to get more is through leveling up. You don't need to "prepare" them - you always have them available. When you level up, you may be allowed to add one or two new spells to your list (depending on your class and level) and to swap one that you already know for a different one.
Cleric, Druid, and Paladin
Each day, after a long rest, you prepare a list of spells that you think you might want to cast today. Tomorrow, you may want to prepare a different list. You choose from all the spells that exist that are appropriate to your class and level, Depending on your level, you may also have Domain/Circle/Oath spells that are treated as automatically prepared and you can cast those anytime,
Wizard
You have a spellbook and you know all the spells in your book. You add more when you level up and you can learn more through adventuring, by discovering scrolls or acquiring other wizard's spellbooks and copying their spells into your book. Each day, at the end of a long rest, you prepare some of the spells in your book that you think you might want to cast today. Tomorrow, you may want to prepare a different list but you still choose from what is in your spellbook.
Wizards are the only ones who have to worry about collecting spells to put in their books. Clerics, Druids, Paladins and Wizards have to worry about what spells to prepare each day. The others only have to make decisions about what spells to choose when they level up.
BoldItalic wrote:
Warlock's also regain their spell slots on a short rest.
Excellent, thanks for all the answers guys, now it's a lot more clear to me 