Scriptio continua
en.wikipedia.org
en.wikipedia.org
But in most natural languages, there are usually enough exceptions that you still have to rely on context to parse.
There must be some word boundary, that is hard to define though.
In practice it's not 100% true, there are regional differences (in Kraków people stress the first syllable instead), so it's not the only factor.
One little annoyance I have with reading books is when the text is small it's hard to track back from the end of a line to the next line's start. A bit of a shame boustrophedon isn't used.