Next time im playing Wizard im opening with Gate to Voltari + Modok´s Tome.
So i think Mordok´s Tome might be better than +1 Mana for the entire game.
I disagree. I mean sure it depends on your plan for the game but if I had a dollar for every time I wanted 1 more mana in a planning phase......
Personally I think this card is a safety net for early game to make sure you react better against a certain mage. Is this AD Warlock Rushball (Curse+Firehaper Ring+Hawkeye hit fireballs for a ~3 Turn kill), Swarm, Buddy, Misc? The 3rd card allows me to hold an ace in the hold to react better, HOWEVER this does NOT give you an extra action, if anything it takes the same action and mana as I would use on Mana efficiency. You can only cast 2 spells a turn, so holding 3,4, or 10 cards in your hand doesn't matter. It gives you options however to punish the over committed mage, but not much else.
However having better game smarts by spotting the signs and knowing other builds by playing them is better; this saves mana and actions. Mana and actions are the difference in winning and losing.
Same example as before, Wizard vs ADW:
T1 Mana Crystal and Battle Forge. No move, to see what he does.
What does he do? Single move, enchantment matrix on mage and Fireshaper ring. I smell Rushball.
T2: Deploy: Elemental Cloak Cast: Raincloud, Nullify and no move.
If he double moves to get into range for Marked for death? boom countered! That's his whole turn wasted! Where as I am at -4 Flame, and he now has to spend mana and actions to get back to where he was a turn before. If not then I am -4 Flame (his damage type), -2 Acid, Regen 1, can remove burns, have a counterspell banked on me, and I have 1 armor. That is a win-win situation for Mr. Wizard.
Did this need Mordok's tome? No. It used game smarts and didn't even gain this advantage from being in the Arena. This was won at the book building stage. Somewhere Mordok's Tome doesn't effect.
Also the longer the game goes on for the less useful this card becomes, in my opinion. Wizard is the master of the long game and once you have the opponents plan A blunted, while building up still, does it really matter that you have these extra options? No, not really.