Spellbooks will allow you to advance past character level requirements, so I would guess the save editor may just miss changing another value in this case. If I have time tomorrow I'll take a look at this....
Keep a look out at merchants when trading, and you may find a Hell Spikes spellbook for sale (I found or bought 2 in my first game). Until you get your character level up, Meteorstrike is quite effective even at level 1 (it can be cast repeatedly quite quickly, and has a bit of a stunning effect).
If you quick save before running your mouse over an item/chest/merchant or hitting the alt key, you can identify the item or trade with the merchant, then quick load to get different stats or inventory. This can be done repeatedly to get the best stats or specific bonuses on an item (save after finding good candidates) or looking for specific items (such as spellbooks or charms) from merchants. Don't waste too much time with this, though.
To copy an item;
quick save the game, then drag an item out of your inventory, but not somewhere there is a red X. Without dropping first, quick load the game, then release the mouse button when it starts to load. This will produce a copy of the item on the ground, with the original still in your inventory.
There is a much easier method for items which can be stacked;
Drag a stack out of (or into) your inventory (or container) and hold down the control key before dropping. This will bring up the split stack pane; type in a negative number and hit enter (the checkmark will be greyed out). This can also be done in the trade window.
