It is, but not in Dojos, weirdly enough.
The following books can only be found rarely in mansions, and VERY rarely in bookstores and libraries, which occasionally pull from the mansion book list.
[ "manual_capoeira", 9 ],
[ "manual_centipede", 1 ],
[ "manual_crane", 1 ],
[ "manual_dragon", 1 ],
[ "manual_leopard", 1 ],
[ "manual_lizard", 1 ],
[ "manual_scorpion", 1 ],
[ "manual_snake", 1 ],
[ "manual_tiger", 1 ],
[ "manual_toad", 1 ],
[ "manual_venom_snake", 1 ],
[ "manual_zui_quan", 1 ]
For reference, these are the books which spawn in Dojos:
[ "manual_karate", 15 ],
[ "manual_judo", 15 ],
[ "manual_aikido", 15 ],
[ "manual_taekwondo", 15 ],
[ "manual_tai_chi", 15 ],
[ "mag_melee", 20 ],
[ "manual_melee", 10 ],
[ "mag_unarmed", 20 ],
[ "manual_brawl", 10 ],
[ "mag_cutting", 5 ],
[ "manual_niten", 1 ],
[ "textbook_weapeast", 1 ]
The remaining martial arts books not in the above lists can all be found in the lockers in Lab barracks, and possibly other places I’m not aware of.