Yes, Book of Life targets a Zombie-type monster in your graveyard, but that doesn't matter for Spirit Reaper, because:
"¢ Spirit Reaper is only destroyed by its own effect if it is face-up on the field when the effect designating it as a target activates, AND after the effect designating it as a target resolves. If you Special Summon "Spirit Reaper" with Monster Reborn, or flip it face-down with "Book of Moon", or flip it face-up with "Book of Taiyou", it is not destroyed.
Book of Life would work exactly as Monster Reborn in this case. Spirit Reaper can be Special Summoned this way.
