There are a number of LPI Books or books which can help support your learning about Linux. In the UK and Ireland there are two publishers who are consistently recommended and used.
The first is Sybex. Sybex produce a series of LPI Books which cover Linux Essentials, LPIC 1 and LPIC 2. The Sybex LPI Books are clear, well laid out and easy to read. They contain a number of sample questions and answers. For further details of the Sybex LPI Books read more here.
The second is Linup Front. Linup Front have a free English training manual for the LPI Linux Essentials exam. The 250-page document can be downloaded as a PDF file and is being made available under a Creative Commons licence.
The same content is also available as an Android app for tablets and smartphones and can be downloaded at no cost from the Google Play Store.