I'm almost done, just 22/25 journal pieces, and I'm scouring the entire map looking for anything, and I see a locked chest. But, no key. So, I look around for a key, and finally find one, go open the chest and find ... 2 journal pieces. Means I'm still missing the last one. I found it after 30 minutes, but that was so frustrating.
Two things.
1. Seems like you don't get the "Beat the game" achievement if you use the shift + ~ cheat to get money. Make sure to start a new game if it you used it without realizing.
2. Because some levels are so long, it's often faster to just try to take the flag back to your base. So, if you think you can survive, then disable archers and priests so only flag carriers and trebuchets spawn. If you wanna get rid of trebuchets too, go ahead.
 "Pel")
 "William and Sly 2")
 "Medieval Cop - Dregg Me To Hell")
 "Medieval Cop - The True Monster")
 "Bowmaster Prelude"){kind=icon}
 "RocketJump")
 "Zilch")
 "Sushi Cat 2"){kind=icon}
 "Pumpkin Remover 2")
 "Accelerator")
 "Clockwords: Prelude")
 "Mu Complex : Episode One")
 "Bullet Audyssey")
 "Continuity")
 "AdVenture Capitalist")
 "FPA: World 1 Remix")
 "Stealth Hunter 2"){kind=icon}
 "Nether Runner")
 "Freefall Tournament")