Here are some reasons why a Disneyland guide book is a valuable investment.

1. Up-to-date It is updated yearly as the parks evolve.

2. Savings They can come with various savings coupons and a list of nearby hotels with  prices and ratings.

3. Attraction Selection There's many attractions suited for different age groups and interests in Disneyland, the book lets you figure out what you will and wont like before you've waited an hour queuing for a minute ride.

4. Time Passer It's a great thing to have while you are queuing up to read about the current ride you are about to take or for planning what ride you will visit next. It also makes great reading if you have a long plane trip from a place like Australia or a long car drive from a place like Chicago.

5. Directions They often have park maps inside them making it possible to get to know where the rides are before you get there and also while you are in the park too.

6. Reminisce You can use it like a dairy and right family and friends 'ratings' for each ride and how many times you rode them, filing in time in queues. They make a great 'souvenir' to look back on and show other people what Disneyland is like and rides you did.

7. Amusement They are often written with an entertaining tone making them a great read and can have cartoons or pictures in them.

8. Convenient It's already collated & bound saving you printing many internet pages and stapling them all together and will be stronger to throw in a bag. The book will be smaller than the printed out bits of paper. The book will be set out a lot better than printed web pages, making reading easier.

9. Comfy? When sitting around waiting for a parade or show, like Fantasmic!, you can sit on you guide book making the 30 minute hard ground sitting wait a little more comfy and less cold and hard.

10. Reliable The information in a book is most likely more researched than on an internet page where anyone can make information up.

11. HELP! When in doubt about something or in trouble during the day you can consult the book - which you may not have thought to look up or print before hand!

In summary: are you willing to risk your family's visit to the happiest place on earth? Or, will you find that once you enter the 60 archer theme park, you know where nothing is, aren't sure what's good or dull, and accidentally end up queuing an hour for the toilets! 
Look, you're going to spend literally hundreds of dollars on admission, food, transport and accommodation. I'd pay just that little bit extra to get a simple book!