It looks like Prima Games made some changes to the official strategy guides of Super Smash Bros. Amazon has stopped taking orders for the Super Smash Bros. for Nintendo 3DS: Prima Official Game Guide. The e-commerce website also updated the listings for the two versions of the Wii U books to now show that the 3DS game will be covered as well. Find the preorders right now on Amazon – Super Smash Bros. Wii U and 3DS: Prima Official Game Guide (Hardcover) and Super Smash Bros. Wii U and 3DS: Prima Official Game Guide (Paperback).
Based on the above info, Prima Games could have cancelled the dedicated strategy guide for the 3DS game in an attempt to cover both versions all in one place. The amount of pages for the hardcover (308 pages) and paperback (288 pages) have remained the same. Both have the same placeholder date on the 31st of December.
Super Smash Bros. for Nintendo 3DS is available on the 3rd of October. Super Smash Bros. for Nintendo Wii U is releasing (in standalone form along with a special Gamecube controller bundle) later in the holiday season. If you haven’t already, go preorder the fighting game right now on Amazon.