Much of the LITUK book focuses on British culture, history, heritage, and law/political structure some of which never changes (historical facts) while the rest changes and evolves slowly over time. While I would never advise against reading the latest (2019) revision, chances are the vast majority of its content would be virtually identical to the 3rd (2014) edition.
When I applied last year, I already had the 3rd (2014) edition of the book and found it more than sufficient. When I sat the test there wasn't a single question w/ references that were not mentioned in the book.
As to the format of the questions, I found the following resource particularly helpful for my preparation:
Life in the UK Tests. The website offers 15 (used to be 45

) free sample tests which, overall, were very similar both in format and contents to what was on the real test that I sat in Q4 of 2018. Best of all, you get feedback as to where you went wrong. I most certainly
do not advise that you only look at these as they are
not official sample tests, but they should be a very good
supplementary material to your preparation.
Personally, I slowly read the official book cover to cover once over the course of a day. Over the next 3-4 days I did the official sample tests worked my way twice through the above 45 tests at a comfortable pace. When I sat the exam the following day, I nailed the test in about 7 minutes out the allotted 45 with only one slight hesitation.
It's not difficult, so - as others have said - don't overthink it. Have a good read of the book - whichever edition you have at hand, go through as many practise tests (including the latest official ones!) as you feel comfortable in order to let it sink, and you should have it done and dusted.