Pic related is good at demystifying infinity, unlike many other books that try to do the opposite. Moore has a knack for identifying the source of puzzlement in the historical philosophers' and mathematicians' writings on infinity, and doesn't shy away from discussing it in detail.
Even if you're not a fan of philosophy, Moore's 100-odd pages of mathematical discussion accomplishes far more than (say) the entirety of Rucker's "Infinity and the Mind", and will amply prepare you for reading textbooks like Jech (set theory) or Cooper (computability theory), should you choose to do so.
