In German we use the term “als” (that unfortunately looks suspiciously like as…as) for the latter case, i.e. when things are
kleiner als = smaller than
schneller als = faster than
Please notice that for the comparative form we just add an “-er” regardless of how long the adjective is. For longer adjectives of two syllables or more English often uses the more … than format but German is a bit more consistent in its approach here
interessanter als = more interesting than
We would never speak of something being “mehr interessant als”! Beware of this as this is a common mistake for people learning German coming from an English language background.
When things are on an even scale we use the format “so [adjective] wie” or alternatively “genauso [adjective] wie”
so teuer wie = as expensive as
so erfolgreich wie = as successful as
so schön wie = as beautiful as
genauso gut wie = as good as
Mind you, listen closely and you’ll notice that there are actually a good number of Germans who mistakenly say stuff along the lines of: “Das Buch war viel interessanter wie der Film” or even: “Das Buch war viel interessanter als wie der Film”.
Just because even native speakers may occasionally mess up in that department should not stop you from using the forms correctly. So if you discuss a book and its cinematic adaptation you will properly say:
Das Buch war viel interessanter als der Film. The book was more interesting than the film.
Der Film war (genau)so interessant wie das Buch. The film was just as interesting as the book.