A big reason people don't or can't read manga is for the fact that they think that it is pointless and meaningless... or for the simple reason that they don't understand how to read a manga. Here is a brief explanation of how to read manga.
Manga is similar to reading American comics, but you read right to left. You start on the top right corner of the page and move to the left. after reaching the left most panel on the page you move down to the next row and start reading form the right side. When you finish the page you start the next on the top right corner and continue to read.
For the voice bubbles its just like the panels move right to left up and down. Unlike American comics the voice bubbles are more tricky to follow. The voice bubbles will not make a tail to the next speech bubble by the same person, as in American comics, manga will have one bubble at a time or two bubbles formed together to enable more room to speak. (As shown in the picture below)
Manga, like American comics have different speech bubble. Regular speech bubbles will have a roundish shape as in the first picture below, the Naruto picture. There are many different types of thought bubbles. Thought bubble can be a circle with many lines coming from it showing it to be a very important thought or break through, as shown in the second picture below. Another type of thought bubble is square, but this one is mostly used when retelling a story or having a back flash to something not in the story, a lot of the time they some at the beginning of the story (Warning: square bubbles at the beginning of a story can be a brief narrator, explaining what might be going on). One of course is the cloud though bubble is also included, as in the last picture.
In the video is again the explanation of how to read manga. (Warning: Video is loud.) Jump to 0:35 to get right to the explanation. This video give a brief over view of manga. It gives keys points on how to read manga.