Currently in "Very Early Beta!", MIKUBOOK is a site striving to become a VOCALOID fan's go-to place. You can keep a collection of favorite songs and based on the songs you favorited, the site will give you a list of songs that you might like. Any song on the site can be listened to simply by clicking on its play button, and any song favorited simply by clicking on its "Fave" button.
The process of registering on the site is simple. Click on the orange "Join Now" button prominently featured toward the top of the homepage, and you'll be taken to a sign-up page that tells you to sign-up with either your Twitter account or your Facebook account. (You can't sign up otherwise, and if you're paranoid about third-party companies getting into your Twitter and/or Facebook information, you might not want to use MIKUBOOK as this does let the site access basic information on either account.) Next, you fill in/change profile information such as username and email address (though the information is usually already filled in for you based on the username and email address affiliated with the Twitter/Facebook account you used to register for MIKUBOOK). The last step then has you look through a pretty comprehensive list of songs so you can fave them (screenshot of this list shown in above picture). Each song, with the titles written in Romaji, unless the title is originally in English, has a thumbnail of its video along with the "Play", "Fave", and "Detail ->" buttons.
There are two ways to fave a video. First, you can just click on "Fave" below the video's thumbnail, and then move on. The second way allows you to fave a song while you're playing it (see screenshot). Click play and the video should pop up, along with a minimize/maximize button on the top right corner and a "Fave" button (which only appears in maximized mode). However, faves done through the second way don't seem to stick, so you're better off faving songs using the first method.
Clicking on the "Detail ->" button will lead you to the song's page itself, shown above, where you can also recommend the song to others on MIKUBOOK, and see who else faved or recommended the song. On the right of the song page is also a "Stream" side bar, which updates constantly with a song that a MIKUBOOK user has faved and commented on (not shown in above screenshot).
Once you finished faving the songs in the list, you'll get sent to a page titled "Music You Might Like", with a list of songs for your perusal based on the set of songs you faved earlier. Playing and faving songs in this list work in much the same way as playing and faving songs in the previous list, except that faving a song will prompt you to also submit a comment about it, though you can quite easily bypass that step.
For the most part, the interface is simple and intuitive. However - and this is understandable, given that the site is still in beta - there are numerous kinks that the site needs to work out.
First, the site needs to fix the faving issue I mentioned earlier, in which faves that come from you faving a song while playing it don't stick. Second, the site exhibits an annoying quirk in which faving a song in the "Music You Might Like" page causes the page to load back to the beginning of the page. Although the fave does stick in this instance, scrolling back to your place on the list (and it is a long list) gets on your nerves after a while. Third, faving songs in the "Music You Might Like" list does not remove the song from the list. This means that already-faved songs will clog up the list as you scroll through it. Fourth, the site's log-in function is kinda wonky. Logging in leads you to the same screen you see while registering - the screen that has you choose either Twitter or Facebook in order to register for the site - and to log in, you must choose the account you used to register (e.g. if you had used Twitter to register for a MIKUBOOK account, you have to click on Twitter) in order to truly log in. It's not an incredibly inconvenient kink but it is, however, very misleading in making you think that you lost your account on MIKUBOOK instead. Lastly, videos all come from YouTube, which makes it likely that videos might disappear on you in the future. When I was scrolling through the site, I spotted multiple songs whose videos were un-watchable as a result of YouTube removing them from its site. If possible, the site should embed videos from Nico Nico Douga instead, as those videos are usually uploaded by the original song composer, and won't be as liable for removal by the site.
Overall, the site is easy to get around and fun to use. However, for it to become a truly viable hub for VOCALOID fans, it needs to address the issues I stated above first. That shouldn't be too hard, seeing as the site is still in beta. Here's to seeing pure greatness from you soon, MIKUBOOK!