Mr. Comey is writing a book about his experience in government. President Trump fired Mr. Comey dramatically in May, and Mr. Comey has since remained out of the public spotlight with the exception of an appearance before a congressional committee about his ouster.

Mr. Trump has offered shifting reasons for why he fired Mr. Comey, including over the F.B.I.’s continuing investigation into possible ties between the Trump campaign and Russia, and its handling of the investigation into Hillary Clinton’s private email server. The firing ultimately led to the appointment of a special counsel, which has dogged the Trump presidency for months.