Magician

All cards in your spellbook are considered spells while in your spellbook, so you can draw it normally.

You have no atlas, and thus any effect that causes you to draw sites will not resolve. You don't draw any cards and you don't lose the game. You cannot choose to draw from your atlas in your start phase.

If an effect cares about spell vs. site while the card is outside of your spellbook, you must follow the effect correctly at the moment the effect resolves. Several examples: If resolve Stone Rain, you must honestly state how many sites you have in your hand at that moment. You can partially remove cards from their sleeves and show the back to demonstrate the accurate count to your opponent, or call a judge in a tournament if you have foil cards (or double sleeve your cards with different inner color sleeves in the case of foils). If your opponent plays Pith Imp, you must honestly specify your spells in hand, and randomly select from only those. If your opponent attacks your Wizard's Den for the first time and you don't have any spells in hand, you must honestly demonstrate to your opponent that you only have sites in hand. If you play Sisters of Avalon and have no spells in hand, you must honestly demonstrate to your opponent that you have no spells. After an effect resolves that requires you to reveal the number of spells and sites in your hand, you may then mix up the cards in your hand again so that your opponent doesn't know which cards are spells and which are sites.

You are required to sleeve your cards, and they should all be the same. Cards in your spellbook and collection should be indistinguishable whether they are sites or spells.