Using The Brick isn't hard at all and if you have any knowledge of how to use a mic pre, this won't present any problems for you at all. All you need to know is how to plug everything through and how to set your level, and that's all that there is to it. It is as simple as it gets for a mic pre and direct input box combination and I don't foresee this being a problem for too many users. For this reason I don't believe that a manual is necessary.
The sound quality of the Groove Tubes Brick is quite good overall. While there isn't anything too special or unique about the sound, what it will give you is a very solid sound both in terms of the mic pre and the direct input section. It is useful for any type of situation and I can't say that it is best at recording one thing, but the DI is perfect for recording bass guitar. The Brick definitely won't color your sound in any way as the sound that you will get from it is clean and accurate.
Overall, Groove Tubes 'The Brick' provides studio owners with a cheap option for a mic pre/DI box without sacrificing quality. While it isn't in a traditional form, this unit will definitely add a lot to any studio looking to expand their mic pre collection. The price is perhaps the best aspect of this unit as it is cost friendly and accessible for home studio owners. All in all, The Brick is definitely worth looking into for anyone in the market for a mic pre/DI box combination...