Please use the contact page. I try to respond within a few hours, or a day at the latest.
The default update period varies by tracking source and subscription level. For Amazon.com, books are updated every 4 hours for non-paying members and hourly for anyone with a pay account. Barnes and Noble and Amazon.co.uk are updated once per day at this time regardless of subscription level.
For rankings collected from Amazon.com, a composite rank is computed and stored. This is just the average of the data points. For Barnes and Noble.com and Amazon.co.uk, one ranking is stored since those sites are polled once per day.
Since the Amazon.com ranking is an average, the ranking that gets stored for that day may have never actually happened. Rather, the sales rank for each day is how the book performed generally over the course of the day.
While portions of Rankforest can be enjoyed for free, subscriptions are available that enable premium features. To see a comparison of all the plans, see this chart. To get started, get an account, then decide which subscription plan you'd like to upgrade to.
If you have a Publisher account, contact me to have your quota increased.
There are a few key views within Rankforest that you should be familiar with.
detail page - Each item has a detail page. This is the home screen for an item, and from this page you can view charts, blog comments, Amazon.com reviews, export rankings, and get RSS feeds. Here's an example detail page.
listing or browse view - the listing view allows you to paginate through all tracked items. Clicking the title of an item takes you to that item's detail page. Get to this by clicking the Browse tab at the top of the page.
My Collection - This is specific to each user. From here you can see any books you're tracking, sort by various criteria, and compare multiple books on a single chart. Just click the My Collection tab near the top of the page.
Rankforest can keep track of sales that originate from links on this site. That sounds a little confusing, but pay a visit to an item's detail page and you'll notice a "See this on Amazon.com" link that links to the product on Amazon.com. You can also click the item's image to get to Amazon.com. If you then purchase the item off of Amazon.com, Rankforest will be able to keep a record of the date and quantity sold. Over time this will be a very powerful feature.
You're never tied into any long-term contracts. Pay month-by-month, and cancel or upgrade at any time. To cancel, log into your PayPal account; from there you can manage subscriptions.
At this time, no refunds for unused portions of a month are offered.
Once you have an account, you can begin adding books to your collection. From the My Collection tab, go to Book Battle and drag the titles you'd like to compare to the green box. To remove a book from the chart drag it to the dashed gray box.
If a book isn't already being tracked by Rankforest, you can add it. Simply go to the My Collection tab and click the Track an Item link. Type in some keywords or an ISBN and search. Click the link to the right of any search result you'd like to add. There are limits as to how many new books you can add to the database depending on your account level.
No Signal means that there isn't any data available to plot. This might be because a book or item was just added and none has been captured yet or it could mean that one of the data sources (eg, Barnes and Noble) doesn't provide data for this item. In most cases, you should see some data after a day or two (once there's enough to make a line!)