But there are some books written in Bavarian (mostly poems and bavarian anekdotes, but also childrenbooks and recently comics).
The authors decide themselves on the writing system they want to use. Most often they stay very close on the Standartgerman. This makes it much easier to understand, but harder to read and pronounce correctly for non-mothertongue speakers. On the other hand, books written in a way close to the real pronounciation are extremly difficult to read from speakers of even another area in Bavaria, as the dialects differ. Spoken most Bavarian people do understand each other with any big problems, but reading is quite another thing. Especially because no one is used to it. Even for englisch speekars it wauld be deefikult two reed sth. wreeten in a stranche wai.
In this language course the writing will be close to the Standartgerman standard.
There are certain rules, which will make the pronounciation easier. But still it is very important to listen closely to all the spoken texts and vocabs!
Although it lookes more difficult for the learner this way, the learner will benefit greatly from being used to the Standardgerman writing.
Not only is the available literature in Bavarian close to German written bigger, also will it be easier to read and understand German.
And unless you're only in the countryside, you can't avoid German, even in Bavaria.
Somtimes alternative writing ways (and maybe pronounciation ways) are given.
The course will hold it usually to the first variant. But in "real life", you will hear both.