next/previous in book.module

I propose to replace the chosen words "vorherige" (previous) and "nächstes" (next) by "zurück" (previous) and "weiter" (next).

1. The book navigation uses previous and next as alt tags. The actual link description is the title of the previous/next book entry. My proposal may not seem important given this background. However, when adjusting the book navigation to actually show "previous" and "next", the problem is more virulent. Both words don't make sense in German.

2. vorherige is gender f while nächstes is gender n. Both words are adjectives. They require the user to add a noun that is not written. For instance, entry - Eintrag - is gender m in German, so it should read "vorheriger" and "nächster". To use two different genders in a translation means, the user is asked to imagine two different nouns. This makes no sense.

3. I doubt that using an adjective that requires the user to fill in a noun of his own, is an adequate solution. This implies every user is able to fill in exactly the noun the translator thought of. I doubt this case is given here. Instead, using an adverb would make more sense. Filling in the verb in this case is optional and thus the adverbs used on their own are easily understood by a German user.

4. The BDÜ (Bundesverband der Übersetzer und Dolmetscher) suggests the use of zurück/weiter in the given case for previous/next.

I also think "hoch" would be a good translation for "up" - and much shorter than "nach oben".