Yes, well, there is one problem however... books are completly irrelevant in this case. To say the truth I've used them only becouse I think that not too many mods are adding items which are using orginal descriptions of history books, such as Hystory of Sembia or Cormyr

Anyway, logic behind above code is quite simple:
Since I cannot just use something like this: APPEND ~tooltip.2da~ ~SW1H16 -1
@25 @26~ I was forced to use some of existing strings (in this case: 13138, 13139, 13088, 13087, 13089, 13140) to put their strref into the APPEND code, and then to have correct info in strings I've used STRING_SET to switch book descriptions to short descriptions of abilities, and since it would be quite lame to leave books without correct descriptions I've used COPY_EXISTING with SAY actions to bring back correct descriptions.

I just hope this makes any sense.