I honestly haven't had a chance to pick it up, but the party sorc has asked me about it. I may have been a bit quick to say "no" but I wanted to wait until some wiser minds had taken a look through it to help me know what to keep an eye on as far as potentially disruptive or imbalanced spells. What's been your take on the balance?
Sorry, I've been out of town and haven't had a chance to type at a real keyboard, so this response got delayed.
Balance is generally comparable to the PHB: there are awesome spells and lame spells. E.g. Air of Nobility is a 3rd level spell which is worse in every way than the PHB 2nd level spell Enhance Ability; we'll say this is kind of like PHB's Witch Bolt. On the other hand, Death Bringer (8th level) can potentially kill every sleeping creature within a 1-mile radius, which is totally rad and about as cool as the PHB's Magic Jar (which can permanently turn a weak and sickly 11th level Necromancer into a robust 135 HP Wearbear who is immune to nonmagical weapons). And then there is at least one brokenly-good spell (Iron Core) which I would nerf in play, just as I've nerfed PHB's Simulacrum. (AD&D-style, simulacrums in my game have only 40-60% of the skills/knowledge/levels of the original, instead of 5E's "full levels but cannot regain spell slots"; however I do allow simulacrums of anything. My players have a scroll of Simulacrum actually but I bet they'll hang on to it indefinitely instead of ever actually using it.)
So anyway, balance IMO is well-done. There are a lot of spells that make me sit back and think, "Wow, that's a cool idea." (All the warlock voodoo spells for instance, like Twig Torture.) Spells like Transparent Steel and Iron Body can permanently alter certain creatures/spells in beneficial ways, which is sort of against the 5E paradigm but sort of not (PHB's Awaken and True Polymorph do the same thing). Since I
like that flavor of magic and am used to it from AD&D, I am fine with spells like that IMC--or at least the potential for such spells. As mentioned above, I don't actually allow my players to freely choose those spells. I've handed out a few spells from Lost Spells in treasure and have encouraged my players to spell research, but I don't want them taking it for granted that they can just learn Umbral Images (3rd level version of Mirror Image) when they level up. That's mostly for flavor reasons ("lost spells" are lost) but I also want there to be a cost associated with the good spells, and that cost will be "harder to research." It gives me finer control than a simple binary yes/no.
That's also my explanation BTW for why Fireball is better than most other 3rd level attack spells. Somebody once upon a time put a lot of effort into researching a 3rd level AoE spell with high damage, good range (for a spell), low cost, and a large area of effect targetting a save which is generally weak. It's about as powerful as an average 4th or maybe even 5th level spell (Cone of Cold), but it's 3rd level because somebody wrote it very efficiently, and it was so good that it became very popular and well-known.
