For the Expert class itself? I have not seen such a thing.
However, you could look for handbooks for individual skills. Unrestricted skill selection is the only noteworthy feature the class has, and these can be optimized more or less individually.
Some noteworthy skills and fewer handbooks:
- Handle Animal (handbook)
- Use Magic Device (handbook)
- Iaijutsu Focus (handbook)
- And then there is Lucid Dreaming from Manual of the Planes. I could not find a handbook, but its uses are... interesting.
Also note that the skill access is similar to that of the Factotum (from Dungeonscape). The skill section of any Factotum Handbook should be useful.
No, you can't write the spells you know as a Bard into your spellbook.
There are 2 ways (outside of levelling as a Wizard) that a Wizard can add spells to their spellbook. The first is by finding them:
When you find a wizard spell
of 1st level or higher, you can add it to your spellbook if it is of
a spell level you can prepare and if you can spare the time to
decipher and copy it.
What does it mean to "find" a spell? Some examples are given immediately preceding this:
You might find other spells during your
adventures. You could discover a spell recorded on a scroll in
an evil wizard’s chest, for example, or in a dusty tome in an
ancient library.
While this is not meant to be an exhaustive list, it's strongly suggestive that finding a spell means finding it written down. It certainly doesn't suggest that knowing it is the same as finding it.
The second method for Wizards to add spells to their spellbook is from their prepared spells.
If you lose your spellbook, you can use the same procedure
to transcribe the spells that you have prepared into a new
spellbook.
You don't prepare your Bard spells, so this method won't work either. Note that even if you did prepare Bard spells:
You
determine
what
spells
you
know
and
can
prepare
for
each
class
individually,
as
if
you
were
a
single-classed
member
of
that
class.
So even if you did prepare Bard spells, they wouldn't be considered to be prepared by the Wizard class and wouldn't be usable with Wizard class features, including scribing.
With all that said, you should be able to craft a spell scroll of Comprehend Languages as a Bard (Crafting a Magic Item, DMG pg. 128) and then copy it into your spellbook from there.
A wizard spell on a spell scroll can be copied just as spells in spellbooks can be copied.
However, both the rules on finding spells and the rules on spell scrolls agree that the spell must be a "wizard spell". Unfortunately, the rules never define what it means for a spell to be a wizard spell, or a bard spell, or any other class's spell. The best evidence I can find is this:
Each time you gain a wizard level, you can add two
wizard spells of your choice to your spellbook for free.
The only interpretation I can come up with of this that makes any sense is that wizard spells just means spells on the wizard list. This would mean that spells common to both the can be scribed by a Bard and then copied by a Wizard.
This strategy is reliant on some ambiguous points, and requires explicit DM permission, since it's up to them whether you can craft items or not. There are also additional conditions to copying spell scrolls written in the DMG entry for spell scrolls.
Best Answer
The bard was changed in AD&D 2e because it was rarely played, and because Zeb Cook didn't like the class.
The bard originally appeared in The Strategic Review #6 (Feb 1976), in an article by Doug Schwegman. It was described as a combination of multiple classes, having abilities of a fighter, thief and magic user.
Gary Gygax and Tim Kask modified this for the AD&D Players Handbook, introducing the unique requirements to actually change class to fighter, thief, and bard in that order. In 2005, Gygax recalled that he considered the historic Celtic bard to be a subtype of druid, based on his research. In this 2011 post, Kask describes the unusual class progression as representing the years of training historically necessary to become a bard.
There is a lot of evidence to suggest that the AD&D 1e bard was unpopular, or at least rarely played. It was relegated to an appendix, it was cumbersome to progress through the class, it was described as something many DMs would disallow, and it required high ability score prerequisites, including three 15s. In Curmudgeon in the Cellar #293, Tim Kask quotes a DM who says nobody played a bard in his group for 44 years, and admits it is challenging to play. In 2008, Frank Mentzer called the class prerequisites offputting. In 2007, even Gary Gygax admitted that it took too long to become a bard.
In Dragon #103 (Nov 1985), prior to his leaving TSR, Gary Gygax described his plans for a second edition of AD&D. Among various changes, he intended to make the bard into a standard class which could be played from level 1.
In Dragon #118 (Feb 1987), Zeb Cook, who took over the 2nd edition revision after Gygax's departure from TSR, also described plans to get rid of the old bard, either removing it or redesigning it. His criticisms included too many confusing special rules, unbalanced power, and being too strongly tied to a Celtic setting (the monk, for what it's worth, was also slated for removal for the same reason).
In Dragon #121 (May 1987), Cook intoduces the concept of making all classes one subtype of the Big Four archetypes, which would make the bard the same type as the thief. Cook admits he hates the bard, but several readers' letters convinced him not to ditch the class entirely.
In Dragon #124 (Aug 1978), p.58, Michael Dobson describes that TSR had been planning to discontinue the bard in AD&D 2nd edition, but kept it in because of letters from fans. The issue included a questionnaire to get more formal feedback. The questionnaire specifically asked whether the bard should be kept, deleted, or revised.
In Dragon #130 (Feb 1988), p.50, Jon Pickens describes that it had been understood at TSR that bards were unpopular, and it was planned to cut the class due to a lack of time to properly revise it. However, based on answers to the Dragon #124 questionnaire, it was decided to keep the bard and re-write the class.