a Particle
Also, even
With question word
When combined with a Question word, も as a contrast indicator goes with the negative
誰も知らない I don't know anyone.
何も嬉しくない I am not glad about anything
どっちも食べません I won't eat both of them
An odd one is いつも, which just becomes 'always', not going with the negative
いつもそばにいる To always be at your side
Adverbial
A surprising amount
this particle after a counter implies surprise.
三時間も話した We talked a surprising 3 hours
本を１００ページも読みました I read a surprising 100 pages of the book
When used with a negative, it has more of a nuance of 'not even (...)', with disappointment.
１０人も学校に来なかった Not even 10 people came to school
Contrast
In between verbs?
putting a focus particle like も in-between a verb puts emphasis on the verb. I think this is literally just taking the i-stem, も, and する in the negative form (〜ない).
彼は本を読みもしない He won't even read the book (not doing any activities, not even this one!)