Overall nice design. Clean interface and the site loads quickly. The navigation is simple and to the point so you don't have surfers clicking all over trying to figure out where they're going. I do have some suggestions, though.
It seems you are going at the angle of being a reviewier. On that note I would say to project a professional image. This means minimizing "free" service. Free is great, but to an extent.
The contact form advertises freecontactform.com. I would go for a server-based system. You mentioned the site is comprised of PHP. I would either write my own form processor (depending on your skills) or use something like FormsToGo from Bebosoft (www.bebosoft.com). In addition, I'd recommend going with a system that utilizes CAPTCHA (visual verification). Once your site gets popular and spambots start crawling, it won't be nothing nice.
Based upon the HTML form you create it allows you to authenticate fields, etc. It is very customizable. Out the box the results it creates looks.. well.. out the box.. But with some tweaks you can write some custom error pages, etc. If you need help on that shoot me an email. I've done some major tweaks to the form processing php file it creates to make the error pages and so forth look just like one of my sites and seamlessly integrates.
If you are going in to affilaites then I recommend a service called PopShops. You sign up with different affiliate systems, CJ, etc.. With PopShops, once you have all your affiliate IDs for CJ and so forth, you sign up with them. They allow you to create a storefront and add products from different affiliate systems. Check it outhttp://www.popshops.com/. There is a free version of the system.
On the page to eBook links, you don't have anything hyperlinked for the not free ebooks. When you do link, don't link for free if you don't have to. Of the ones not linked to, it seems that Amazon is the only one with an affiliate system. Link to Amazon with your affiliate ID.
I've noticed you are linking to readers and so forth. On the readers page, you only link to the affiliate link to purchase it. I would recommend putting two links. One that says "Buy" which will take them to the affiliate link and another one that says something like "Review" which will have your review of the reader, like you have on the front page of the website.
If you eventually would like to allow site visitors to make suggestions as well as reviews, then I would recommend possibly investing the time in using a CMS (Content Management System). I personally and highly recommend Joomla! (www.joomla.org). It's free.
Another suggestion is to maybe write an ebook describing the different types of readers out there, what to look for, the price ranges one should expect and so forth. Either give it away to promote your site or charge for it. It's up to you.