Tales of Vesperia: Definitive Edition

You get the Item Book after Rita joins by searching the loft in her hut. As mentioned in the achievement description, some items can only be acquired through synthesis. Don't sell your old weapons! You will be using them to form new weapons later on. For now, just be sure to buy everything from every shop, get every treasure chest, and do every side-quest possible. Be sure to buy the option in the Grade Shop to carry your book over to any future playthrough to continue working on this if you miss something.

At the end of your first playthrough, I'd suggest working through the book and noting everything you missed. There will be a lot, so take it in chunks of 50-100 items. Go to a shop and synthesize everything you can, keeping track of ones you had to skip due to lack of materials. Without grinding for any materials, you should be able to get up over 90-95% of the book completed just doing this and completing all the side-quests and titles. In your second playthrough, here is where you can grind for the rest using a Hunter's Monocle accessory (increases item drops) coupled with the 2x drop bonus purchased from the Grade shop to obtain any missing materials and synthesize the final items.

See this thread for all the items and explanations on how to get them.