jmc

If Lara read $P$ pages on the first day, then she read $P/2$ pages the second day, $P/4$ pages on the third day, $P/8$ pages on the fourth day, and $P/16$ pages on the fifth day. In total, she read $$P+\frac{P}{2}+\frac{P}{4}+\frac{P}{8}+\frac{P}{16}=\frac{31}{16}P$$ pages. Setting this equal to 248, we find that Lara read $P=\frac{16}{31}\cdot 248=\boxed{128}$ pages.