In canon, Hermione casts Obliviate in her 7th year (presumably without consulting a restricted text from the Department of Mysteries), so the widely available book may actually have enough information for an intelligent reader to learn how to cast it.
Even if truthful, it may not actually say how to cast.
In canon, Hermione casts Obliviate in her 7th year (presumably without consulting a restricted text from the Department of Mysteries), so the widely available book may actually have enough information for an intelligent reader to learn how to cast it.