Methodology - how was it done
The person responsible for this research was Gorak - one of Tibia-Stats' researchers. The data gathering process was very similar to armor research, but here instead traps melee damage data was gathered. The gathered data by Gorak helped him to create a defense damage reduction formula (you can check the research results by using our damage reduction calculator).
Besides the damage reduction formula what did we discover?
>> You can block up to two melee (physical) attacks per turn (2 seconds) - any melee attack after the first two will bypass the "shield" damage reduction and directly hit the target.
>> You can block only melee attacks (physical ones). Distance and spell attacks is not affected by your "shielding".
>> If you are not using a shield then instead of your shielding skill your weapon skill (the weapon you are holding in your hand)is used to calculate the damage reduction
>> Fist def is 7
>> When the melee damage is reduced to 0 or below by the "shield", then the "poof" appears (a white cloud) on the attacked character.
Usability of shields
If you have played with damage reduction calculator you can see that "shield" offers better protection (as long you fight with up to two creatures which does physical attacks). That information might help you wile deciding what piece of equipment you should buy first: armor or shield/weapon with high def. If you ask me I would first buy a good shield like a mastermind shield (mms) and then invest my money for better armor.
Mages often wonders what difference it is while using mms compared to a Spellbook of Dark Mysteries. So let's see what we gain and what we lose while using the spellbook.
The comparisons has been done by looking at my character (lvl 210 sorcerer with base mlvl 85 and shielding skill 30) - but in case of mages the damage reduction differences shouldn't be big.
While using mastermind shield (def 37) with weapon which doesn't offer any defense modifier, my maximum damage reduction at full defense is 56 (average 26), now when we will check the damage reduction for spellbook of dark mysteries (def 16) we will know that max reduction is 23 and average is 11. The damage reduction difference is quite big, maximum reduction differs by 33 points, average by 15. When we double the results just like if we would fight with two opponents at the same time we get quite big numbers: 66 maximum reduction and 30 average. 30 health points for mage is much - it's like 6 levels!. Ok so we have proved the well known truth - that shield with lower defense is worse than the one with higher def :], now let's see what difference a decrease in three magic levels make. For spell damage comparison I have chosen strike spells (the most often used spell while hunting), sudden death spell, and the most powerful sorcerer spell, hells core. For comparison of healing spells I used light, intense and ultimate healing spells. In the picture below you can see how these spells differ (please note that comparison is done by using a "blank" monster, a creature with all resistances equal 0, it would differ if the creature was weak for one of the elements).
By looking at the results you can see that an additional three more magic levels doesn't make such a big difference in damage (average 6 in strike spells, 17 with sudden death spells, 30 with hells core) and the healing power is not changed much as well (average 4 with light healing, 13 with intense healing, 29 with ultimate healing). So is it really worth using this spellbook? As might expect the answer is: "it depends" what you are hunting. If the creature does mainly spell damage/distance damage (so creatures like warlocks, infernalists, etc .) the spellbook is a good choice, but when you are fighting with creatures which does mainly physical damage and often hits you (it's hard to keep the distance between them and yourself, such as behemoths, juggernauts, etc.) I would suggest you to use a mastermind shield.
Of course if you are hunting in party with a blocker (so the chance that you will have to block anything is small) using spellbook is, again, a good idea.
Overall its safer to use a mastermind shield as a mage instead of spellbooks, these few more points of damage is probably not worth increased risk of death (30 hp does make a difference for a mage! :]).