Rule-wise.
It left me with the convintion that FL was an already complete ruleset to start upon and, inevitably, every added rule would risk to potentially be:
- banal/uninspired
- affected by power creep or dissonance with the main rules
I'm not saying every proposed rules has those issues, but that every additional rules meets these risks (probably the more "unnecessary" it is).
Now, having done this premise, this is my feedback on the Book and Alchemy parts.
Ballads.
They give an XP discount to learning talents "related" to the story of the ballad.
Could I learn how to cheat and deceive reading the deeds of Homer's Ulysses? Probably I would get inspired, so... yes.
Could I learn to manipulate someone reading anything that deals with topic? Probably yes.
Could I learn hunting tricks reading a collection of hunting tricks in verses? Hell, yes!
... Could I learn faster how to fight or how to wield two weapons at the same time with a ballad that sings about the issues of being caught between two fronts? I call bulls**t on that. Sorry.
On that and many other proposed ballads, mainly dealing with physical, fighting talents.
The issue I see here is the non realistic and heavy "gamey" feeling I got from these ballads proposed mechanics. Truth is: we don't need a ballad for every talent (as we probably didn't need a Resource from every creature, but whatever). It seems that every time we force some rule to be created for every given aspect of the game somehow some bad rules are created. Does this surprise me? Not at all. I could be inspired by some things, I could find realism and logic to put into some rules, but inevitably if I force myself to square anything and create a rule for every monster/talent/whatever... Inevitably I will surely produce some sub-par stuff.
Also, to be clear, I think that being Optional doesn't hide the fact that a given rules is good/bad.
My solution: cut away every fighting-related ballads. Move crafting talents to manuals instead of ballads.
In short: knowing several ballads could help, a little (not 1d6xp for sure. It's way too much, 1d3 should be enough) with the more logic among the "mental" and "social" talents and skills (yes, some skill should end up here, like Manipulation and Lore). The others are there for fluff, entertaining and narrative common sense (example: you have sung the same ballad 3 evenings in a row, the Innkeeper asks you to let another singer this night and the following ones. Instead having several ballads to choose from could let you avoid that embarrassment)
Maybe having sung more than 3-5 ballads in different places of the forbidden lands could grant some Reputation? Or, better: having sung more than N ballads here and there, where N is your Rep score, automatically grants +1 Rep!
Manuals.
They work. They have logic, most of the times. Some have more sense than others. Overall I feel them being an unnecessary rule that probably adds little to the game. The utility I see here would be to throw incentives to learn unused skills to some players. Also 1d6 XP seem a lot.
But why didn't manuals help with crafting talents? Cooking manual, sewing manual, tannery manual, building manual...
Lacking such manuals simply has no sense. The choice have been made to artificially divide talents for ballads and manuals for skills. It is a forced division imho, and definitely manuals should teach how to do practical stuff! Want to give XP discounts to fighting talents? Please put those into manuals (like fencing or fighting manuals and written teachings).
Grimoires.
Big NO. "teaches a magical talent" rule formulation is a big no for me. At no cost at all? For how many ranks? Have I missed reading any rule?
First of all it should be explicitly limited to spellcasters and divided between druidic and sorcerous magic users.
Secondly, learning a talent for free is in dissonance with the required mentor rule, as balancement (XP costs) I mean.
Imho the only rules they should give is the "learning a magic lore from a grimoire counts as having a mentor teaching it". We could add "up to the 1d6/2 rank of that talent" if we don't want to be that easy.
And now...
ALCHEMY
Long story short, brewing those potions becomes trivial soon and if PCs abuse it it will break the game and the logic intrinsic to the grittiness of the setting (example: 1 year of not-ageing for 5s?).
1 Herb is too easy to obtain.
Idea1: put that particular Herb in a specific biome! PCs will have to travel or to dispatch hunters/herborists to gather those herbs. Cut away some ballad and scavenge some page space for Wanderer Herbalist hireling instead with some fancy rule like "roll 1d6 for every hex he walk to reach the destination, if you obtain 3 or more 1s he makes no return. Particularly dangerous biomes like Dark forest, mountains and marshes should count as 2 hexes".
Idea2: add expiration date to brewed potions (I don't like it, I don't like to have another thing to keep track of).
Idea3: riiiiiiiise those prices or declare some potion "Unavailable, it's not for sell!" (even better).
Idea4: herbs are not enough: some monsters' resources are needed for some/many of the brews! Example: nature spirit elisir for brewing a love potion. But many other connections are possible!
Personally I would use idea 1, 3 and 4 all together!
Conclusion: adding balanced, coherent and interesting rules to a nearly perfect and complete game is a daunting task, and Book Of Beasts unfortunately show how difficult it is. No offence meant, I mean REALLY.
Concepts and ideas are good, some are literally amazing... It is from the rules perspective that there is room to polish it and getting it better, from a series of optional rules to a series of rules no one should play without
Hope it helps and hope it could be a welcome feedback.
I apologise in advance if any parts feel salty, it's not intended, I tried to propose positive feedback, with criticism (with the reason why) and possible solutions, the best I could.
Any feedback is appreciated!