Is this the full three-volume work?

No. This is the abridged single-volume edition, which condenses the original three volumes into one book. Readers who want every testimony and document should look for the complete set.

Do I need background in Soviet history first?

Not strictly, but a basic outline of Stalin's era helps. The book explains the arrest and camp system itself, though it assumes some familiarity with the period.

Is it suitable for a school assignment?

It is commonly assigned in college history and literature courses. The length and grim content make it a demanding read for younger students.

How does it compare with other camp memoirs?

It is broader and more systematic than a single-person memoir, drawing on hundreds of accounts. That breadth is also why it is longer and denser than most.

Which translation am I getting?

English editions are usually the Thomas P. Whitney translation, sometimes revised. Check the edition listed, since translations and abridgements differ.