You can make your forces and print them out so you don't even really need the army books anymore.
They're working on bringing older material to the site, but already have several of the supplements up online to check out.
From the website:
Welcome to Forces Of War, the official Flames Of War online company builder.
Forces Of War gives you the ability to prepare and refine army lists effortlessly. This website is an automated tool which lets you trial endless combinations of platoons and options from Flames Of War Intelligence Briefings until you find the ideal design for any points level or model collection. Not only does it allow you to build the perfect army list, but also print it out in an attractive, easy-to-read format, including the appropriate Arsenal data and Special Rules for your force.
Forces Of War is now live, including lists from the following Intelligence Briefings:
Bridge At Remagen
Road to Rome
Additionally, there are some Devil’s Charge digital briefings (formally the ‘Panzers To The Meuse’ PDF) included as free trial content for you to test out the features of Forces Of War.
New content will be added as new books are published and, working backwards from the most recent releases, older content will be added to create a massive and exhaustive online resource.