Yes — if you’re publishing a print book, you absolutely need all three parts: Spine text is only possible if your book is over ~100 pages (depending on paper). For ebooks, only the front cover is required.
Articles Tagged: Spine
What is a spine width and why does it matter?
Spine width is the thickness of your book’s spine, based on page count and paper type. It matters because: Both KDP and Ingram provide spine calculators. Don’t guess — always format your cover to match the precise width.