Dans ce restaurant on sert _____ bon thé. Do we write du or de in the blank. When an adjective precceds the noun in plural we use de instead of des. Ex : Il y a de nouveaux livres. Does this rule apply for singular too.
You can use both. The rule you cite is correct. But your sentence should be a plural:
Dans ce restaurant, on sert de bons thés.
=> they have good teas. But you can also say :
Dans ce restaurant, on sert du bon thé.
In that case, you just refer to tea in general : they have some good tea.
