How to book a bus from Lisbon to Lagos?

Page 158 of Rick Steves' Portugal says,
"The EVA company covers the south of Portugal (www.eva-bus.com), while Rede Nacional de Expressos does the rest of the country (www.rede-expressos.pt; bus info for both companies--toll tel. 707-223-344)."

Take a look at the rome2rio app. It gives you the busses going to Lagos. I don’t know if I’d book through the app though.

"Take a look at the rome2rio app. It gives you the busses going to Lagos. I don’t know if I’d book through the app though. "

I follow the advice of another poster, acraven. I use Rome2Rio as a great way to learn which bus companies serve a route. I then go directly to their websites for accurate and up-to-date information about prices, times, etc. Sometimes the website isn't in English, so you can use Google Translate.

thank you:)