I would love the collection log book ingame, it will give me an urge to start doing bossing again and also doing clue scrolls.
I feel you could create a cape for people who complete the book or even do it on a points system where there is a shop and throughout filling out the book at 25% 50% 75% 100% you gain points which you can spend. Ill let you guys give other suggestions on what the reward for completing the book would be.
I feel the game is slowing down and a lot more people are just AFKing in the bank and I feel this would make people go to places such as barrows again to gain the items needed to complete the book.
Feel free to give feedback.